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Differential and Integral Calculus by Feliciano and Uy, Exercise 1.3, Problem 7

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PROBLEM:

Evaluate limx1x1x+32 \displaystyle \lim\limits_{x\to 1}\:\frac{x-1}{\sqrt{x+3}-2}.


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 SOLUTION:

A straight substitution of  x=1x=1 leads to the indeterminate form 00 \frac{0}{0} which is meaningless.

Therefore, to evaluate the limit of the given function, we proceed as follows

limx1x1x+32=limx1x1x+32x+3+2x+3+2=limx1(x1)(x+3+2)(x+3)22=limx1(x1)(x+3+2)x1=limx1x+3+2=1+3+2=4+2=2+2=4  (Answer)\begin{align*} \\ \lim\limits_{x\to 1}\:\frac{x-1}{\sqrt{x+3}-2}& =\lim\limits_{x\to \:1}\:\frac{x-1}{\sqrt{x+3}-2}\cdot \frac{\sqrt{x+3}+2}{\sqrt{x+3}+2}\\ \\ & =\lim\limits_{x\to 1}\frac{\left(x-1\right)\left(\sqrt{x+3}+2\right)}{\left(x+3\right)-2^2}\\ \\ & =\lim\limits_{x\to 1}\frac{\left(x-1\right)\left(\sqrt{x+3}+2\right)}{x-1}\\ \\ & =\lim\limits_{x\to 1}\sqrt{x+3}+2&\\ \\ & =\sqrt{1+3}+2\\ \\ &=\sqrt{4}+2\\ \\ & =2+2\\ \\ & =4 \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)\\ \\ \end{align*}

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Differential and Integral Calculus by Feliciano and Uy, Exercise 1.3, Problem 6

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PROBLEM:

Evaluate limx0x+164x \displaystyle\lim\limits_{x\to 0}\:\frac{\sqrt{x+16}-4}{x}.


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 SOLUTION:

A straight substitution of x=0x=0 leads to the indeterminate form 00 \frac{0}{0} which is meaningless.

Therefore, to evaluate the limit of the given function, we proceed as follows.

limx0x+164x=limx0x+164xx+16+4x+16+4=limx0(x+16)42x(x+16+4)=limx0x+1616x(x+16+4)=limx0xx(x+16+4)=limx01x+16+4=10+16+4=14+4=18  (Answer)\begin{align*} \\ \lim\limits_{x\to 0}\:\frac{\sqrt{x+16}-4}{x} & =\lim\limits_{x\to 0}\:\frac{\sqrt{x+16}-4}{x}\cdot \frac{\sqrt{x+16}+4}{\sqrt{x+16}+4}\\ \\ & =\lim\limits_{x\to 0}\:\frac{\left(x+16\right)-4^2}{x\left(\sqrt{x+16}+4\right)}\\ \\ & =\lim\limits_{x\to 0}\:\frac{x+16-16}{x\left(\sqrt{x+16}+4\right)}\\ \\ & =\lim\limits_{x\to 0}\:\frac{x}{x\left(\sqrt{x+16}+4\right)}\\ \\ & =\lim\limits_{x\to 0}\:\frac{1}{\sqrt{x+16}+4}\\ \\ & =\:\frac{1}{\sqrt{0+16}+4}\\ \\ & =\:\frac{1}{4+4}\\ \\ & =\:\frac{1}{8} \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)\\ \\ \end{align*}

 

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Differential and Integral Calculus by Feliciano and Uy, Exercise 1.3, Problem 5

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PROBLEM:

Evaluate limx0(x+3)292x\displaystyle \lim\limits_{x\to 0}\:\frac{\left(x+3\right)^2-9}{2x}.


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 SOLUTION:

A straight substitution of x=0x=0 leads to the indeterminate form 00\frac{0}{0} which is meaningless.

Therefore, to evaluate the limit of the given function, we proceed as follows

limx0(x+3)292x=limx0(x+3)2(3)22x=limx0(x+33)(x+3+3)2x=limx0x(x+6)2x=limx0x+62=0+62=62=3  (Answer)\begin{align*} \lim\limits_{x\to 0}\:\frac{\left(x+3\right)^2-9}{2x} & =\:\lim\limits_{x\to 0}\:\frac{\left(x+3\right)^2-\left(3\right)^2}{2x}\\ \\ & =\:\lim\limits_{x\to 0}\:\frac{\left(x+3-3\right)\left(x+3+3\right)}{2x}\\ \\ & =\lim\limits_{x\to 0}\:\frac{x\left(x+6\right)}{2x}\\ \\ & =\lim\limits_{x\to 0}\:\frac{x+6}{2}\\ \\ & =\frac{0+6}{2}\\ \\ & =\frac{6}{2}\\ \\ & =3 \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)\\ \end{align*}

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Differential and Integral Calculus by Feliciano and Uy, Exercise 1.3, Problem 4

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PROBLEM:

Evaluate limx2(x3x2x22x35x2+5x6) \displaystyle \lim\limits_{x\to 2}\left(\frac{x^3-x^2-x-2}{2x^3-5x^2+5x-6}\right).


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 SOLUTION:

A straight substitution of x=2x=2 leads to the indeterminate form 00\frac{0}{0} which is meaningless.

Therefore, to evaluate the limit of the given function, we proceed as follows

limx2(x3x2x22x35x2+5x6)=limx2((x2)(x2+x+1)(x2)(2x2x+3))=limx2(x2+x+12x2x+3)=22+2+12(2)22+3=4+2+182+3=79  (Answer)\begin{align*} \lim\limits_{x\to 2}\left(\frac{x^3-x^2-x-2}{2x^3-5x^2+5x-6}\right)&=\lim\limits_{x\to 2}\left(\frac{\left(x-2\right)\left(x^2+x+1\right)}{\left(x-2\right)\left(2x^2-x+3\right)}\right)\\ \\ & =\lim\limits_{x\to 2}\left(\frac{x^2+x+1}{2x^2-x+3}\right)\\ \\ & =\frac{2^2+2+1}{2\left(2\right)^2-2+3}\\ \\ & =\frac{4+2+1}{8-2+3}\\ \\ & =\frac{7}{9} \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)\\ \\ \end{align*}

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Differential and Integral Calculus by Feliciano and Uy, Exercise 1.3, Problem 3

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PROBLEM:

Evaluate limx3(x313x+12x314x+15) \displaystyle \lim\limits_{x\to 3}\left(\frac{x^3-13x+12}{x^3-14x+15}\right).


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SOLUTION:

A straight substitution of x=3x=3 leads to the indeterminate form 00\frac{0}{0} which is meaningless.

Therefore, to evaluate the limit of the given function, we proceed as follows.

limx3(x313x+12x314x+15)=limx3((x3)(x2+3x4)(x3)(x2+3x5))=limx3(x2+3x4x2+3x5)=(3)2+3(3)4(3)2+3(3)5=9+949+95=1413  (Answer)\begin{align*} \lim\limits_{x\to 3}\left(\frac{x^3-13x+12}{x^3-14x+15}\right)& =\lim\limits_{x\to 3}\left(\frac{\left(x-3\right)\left(x^2+3x-4\right)}{\left(x-3\right)\left(x^2+3x-5\right)}\right)\\ \\ & =\lim\limits_{x\to 3}\left(\frac{x^2+3x-4}{x^2+3x-5}\right)\\ \\ &=\frac{\left(3\right)^2+3\left(3\right)-4}{\left(3\right)^2+3\left(3\right)-5}\\ \\ & =\frac{9+9-4}{9+9-5}\\ \\ & =\frac{14}{13} \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)\\ \\ \end{align*}

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Differential and Integral Calculus by Feliciano and Uy, Exercise 1.3, Problem 2

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PROBLEM:

Evaluate limx2(x2+2x83x6)\displaystyle \lim\limits_{x\to 2}\left(\frac{x^2+2x-8}{3x-6}\right)


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SOLUTION:

A straight substitution of x=2x=2 leads to the indeterminate form 00\frac{0}{0}  which is meaningless.

Therefore, to evaluate the limit of the given function, we proceed as follows

limx2(x2+2x83x6)=limx2((x+4)(x2)3(x2))=limx2(x+43)=2+43=63=2  (Answer)\begin{align*} \lim\limits_{x\to 2}\left(\frac{x^2+2x-8}{3x-6}\right)& =\lim\limits_{x\to 2}\left(\frac{\left(x+4\right)\left(x-2\right)}{3\left(x-2\right)}\right)\\ \\ &=\lim\limits_{x\to 2}\left(\frac{x+4}{3}\right)\\ \\ &=\frac{2+4}{3}\\ \\ &=\frac{6}{3}\\ \\ & =2 \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)\\ \\ \end{align*}

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Differential and Integral Calculus by Feliciano and Uy, Exercise 1.3, Problem 1

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PROBLEM:

Evaluate limx4(x364x216)\displaystyle \lim\limits_{x\to 4}\left(\frac{x^3-64}{x^2-16}\right)


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SOLUTION:

A straight substitution of x=4 x=4 leads to the indeterminate form 00 \frac{0}{0} which is meaningless.

Therefore, to evaluate the limit of the given function, we proceed as follows

limx4(x364x216)=limx4((x4)(x2+4x+16)(x+4)(x4))=limx4(x2+4x+16x+4)=(4)2+4(4)+164+4=488=6  (Answer)\begin{align*} \lim\limits_{x\to 4}\left(\frac{x^3-64}{x^2-16}\right)& =\lim\limits_{x\to 4}\left(\frac{\left(x-4\right)\left(x^2+4x+16\right)}{\left(x+4\right)\left(x-4\right)}\right)\\ \\ & =\lim\limits_{x\to 4}\left(\frac{x^2+4x+16}{x+4}\right)\\ \\ & =\frac{\left(4\right)^2+4\left(4\right)+16}{4+4}\\ \\ & =\frac{48}{8}\\ \\ & =6 \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)\\ \\ \end{align*}

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Differential and Integral Calculus by Feliciano and Uy, Exercise 1.2, Problem 8

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PROBLEM:

Evaluate limx0(3x+2x22x+4)\displaystyle \lim\limits_{x\to 0}\left(\frac{3x+2}{x^2-2x+4}\right).


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SOLUTION:

Plug in the value x=0.

limx0(3x+2x22x+4)=3(0)+2(0)22(0)+4=0+200+4=24=12  (Answer)\begin{align*} \lim\limits_{x\to 0}\left(\frac{3x+2}{x^2-2x+4}\right)& =\frac{3\left(0\right)+2}{\left(0\right)^2-2\left(0\right)+4}\\ \\ & =\frac{0+2}{0-0+4}\\ \\ & =\frac{2}{4}\\ \\ & =\frac{1}{2} \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)\\ \\ \end{align*}

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Differential and Integral Calculus by Feliciano and Uy, Exercise 1.2, Problem 7

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PROBLEM:

Evaluate limx3(3xxx+1)\displaystyle \lim\limits_{x\to 3}\left(\frac{\sqrt{3x}}{x\sqrt{x+1}}\right).


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SOLUTION:

Plug the value x=3.

limx3(3xxx+1)=3(3)33+1=934=332=36=12  (Answer)\begin{align*} \lim\limits_{x\to 3}\left(\frac{\sqrt{3x}}{x\sqrt{x+1}}\right)&=\frac{\sqrt{3\left(3\right)}}{3\sqrt{3+1}} \\ \\ &=\frac{\sqrt{9}}{3\sqrt{4}} \\ \\ & =\frac{3}{3\cdot 2}\\ \\ & =\frac{3}{6}\\ \\ &=\frac{1}{2} \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)\\ \\ \end{align*}

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Differential and Integral Calculus by Feliciano and Uy, Exercise 1.2, Problem 6

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PROBLEM:

Evaluate limx2(4x3)(x2+5)\displaystyle \lim_{x\to 2}\left(4x-3\right)\left(x^2+5\right).


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SOLUTION:

Plug the value x=2.

limx2(4x3)(x2+5)=[(42)3][(2)2+5]=[83][4+5]=(5)(9)=45  (Answer)\begin{align*} \lim\limits_{x\to 2}\left(4x-3\right)\left(x^2+5\right) & =\left[\left(4\cdot 2\right)-3\right]\left[\left(2\right)^2+5\right]\\ & =\left[8-3\right]\left[4+5\right]\\ & =\left(5\right)\left(9\right)\\ & =45 \ \qquad \ \color{DarkOrange} \left( \text{Answer} \right)\\ \end{align*}

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