A power difference

Calculus Level 3

lim x 1 x + x 2 x 2 + x 2 = ? \large \lim_{x\to1 } \dfrac{x + \sqrt x - 2}{x^2 + \sqrt x - 2 } = ?


The answer is 0.6.

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3 solutions

Zakaria Salameh
Dec 1, 2015

let x=y^2 so as x--->1 y--->1 the problem becomes lim(y^2+y-2)/(y^4+y-2)=lim(y-1)(y+2)/(y-1)(y^3+y^2+y+2) =lim(y+2)/(y^3+y^2+y+2)=3/5=0.6

Noel Lo
Nov 29, 2015

Applying L'Hopital's rule, lim x 1 x + x 2 x 2 + x 2 = lim x 1 1 + 1 2 x 2 x + 1 2 x \large \lim_{x\to1 } \dfrac{x + \sqrt x - 2}{x^2 + \sqrt x - 2 } = \large \lim_{x\to1 } \dfrac{1 + \dfrac{1}{2\sqrt x}}{2x + \dfrac{1}{2\sqrt x }}

= 1 + 1 2 2 + 1 2 = 2 + 1 4 + 1 = 3 5 = 0.6 =\dfrac{1+\dfrac{1}{2}}{2+\dfrac{1}{2}} = \dfrac{2+1}{4+1} =\dfrac{3}{5}=\boxed{0.6}

Armain Labeeb
Jul 10, 2016

Factor x + x 2 x 2 + x 2 \frac{x+\sqrt{x}-2}{x^2+\sqrt{x}-2}

lim x 1 ( x + x 2 x 2 + x 2 ) = lim x 1 ( ( x 1 ) ( x + 2 ) ( x 1 ) ( x 3 2 + x + x + 2 ) ) = lim x 1 ( ( x 1 ) ( x + 2 ) ( x 1 ) ( x 3 2 + x + x + 2 ) ) = lim x 1 ( x + 2 x 3 2 + x + x + 2 ) P l u g i n v a l u e s : 1 + 2 1 3 2 + 1 + 1 + 2 lim x 1 ( x + x 2 x 2 + x 2 ) = 3 5 \begin{aligned} \lim _{ x\to 1 } \left( \frac { x+\sqrt { x } -2 }{ x^{ 2 }+\sqrt { x } -2 } \right) & =\lim _{ x\to 1 } \left( \frac { \left( \sqrt { x } -1 \right) \left( \sqrt { x } +2 \right) }{ \left( \sqrt { x } -1 \right) \left( x^{ \frac { 3 }{ 2 } }+x+\sqrt { x } +2 \right) } \right) \\ & =\lim _{ x\to \: 1 } \left( \frac { \left( \sqrt { x } -1 \right) \left( \sqrt { x } +2 \right) }{ \left( \sqrt { x } -1 \right) \left( x^{ \frac { 3 }{ 2 } }+x+\sqrt { x } +2 \right) } \right) \\ & =\lim _{ x\to \: 1 } \left( \frac { \sqrt { x } +2 }{ x^{ \frac { 3 }{ 2 } }+x+\sqrt { x } +2 } \right) \\ Plug\, \, \, in\, \, \, values\, \, & :\, \, \frac { \sqrt { 1 } +2 }{ 1^{ \frac { 3 }{ 2 } }+1+\sqrt { 1 } +2 } \\ \therefore \lim _{ x\to 1 } \left( \frac { x+\sqrt { x } -2 }{ x^{ 2 }+\sqrt { x } -2 } \right) & =\frac { 3 }{ 5 } \end{aligned}

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