Constant underestimation

Algebra Level 1

x 2 + 5 ( x 2 + 2 ) 2 = 1 x 2 + 2 + m ( x 2 + 2 ) 2 \large \dfrac{x^{2}+5}{(x^{2}+2)^{2}} = \dfrac{1}{x^{2}+2} + \dfrac{m}{(x^{2}+2)^{2}}

Above shows an algebraic identity for constant m m . Find the value of m m .


The answer is 3.

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5 solutions

Ritu Roy
Dec 8, 2014

x 2 + 5 ( x 2 + 2 ) 2 \dfrac{x^{2}+5}{(x^{2}+2)^{2}} = 1 ( x 2 + 2 ) \dfrac{1}{(x^{2}+2)} + m ( x 2 + 2 ) 2 \dfrac{m}{(x^{2}+2)^{2}}

x 2 + 5 ( x 2 + 2 ) 2 \dfrac{x^{2}+5}{(x^{2}+2)^{2}} = ( x 2 + 2 ) ( x 2 + 2 ) 2 \dfrac{(x^{2}+2)}{(x^{2}+2)^{2}} + m ( x 2 + 2 ) 2 \dfrac{m}{(x^{2}+2)^{2}}

x 2 + 5 ( x 2 + 2 ) 2 \dfrac{x^{2}+5}{(x^{2}+2)^{2}} = ( x 2 + 2 ) + m ( x 2 + 2 ) 2 \dfrac{(x^{2}+2)+m}{(x^{2}+2)^{2}}

x 2 + 5 = x 2 + 2 + m x^{2}+5=x^{2}+2+m

m = 3 \boxed {m=3}

Rushi Wawge
Dec 8, 2014

x²+5/(x²+2)²=1/(x²+2) + m/(x²+2)² x²+5/(x²+2)²=x²+2+m/(x²+2)² x²+5=x²+2+m 5-2=m 3=m m=3

Chew-Seong Cheong
May 25, 2019

x 2 + 5 ( x 2 + 2 ) 2 = 1 x 2 + 2 + m ( x 2 + 2 ) 2 Multiply both sides by ( x 2 + 2 ) 2 x 2 + 5 = x 2 + 2 + m m = 3 \begin{aligned} \frac {x^2+5}{(x^2+2)^2} & = \frac 1{x^2+2} + \frac m{(x^2+2)^2} & \small \color{#3D99F6} \text{Multiply both sides by }(x^2+2)^2 \\ x^2+5 & = x^2+2 + m \\ \implies m & = \boxed 3 \end{aligned}

This question can be done by using a method used for solving integrals by using partial fractions.

we have , x 2 + 5 ( x 2 + 2 ) 2 = 1 ( x 2 + 2 ) + m ( x 2 + 2 ) 2 \frac{x^{2}+5}{(x^{2}+2)^{2}} = \frac{1}{(x^{2}+2)} + \frac{m}{(x^{2}+2)^{2}}

We can multiply both sides by ( x 2 + 2 ) 2 (x^{2}+2)^{2} ,doing which we get , x 2 + 5 = x 2 + 2 + m x^{2}+5 = x^{2}+2 + m

solving which we get , m = 3 \boxed{m = 3}

Arpit Goyal
Dec 8, 2014

Take LCM on RHS, then lower part of both side will get canceled. The equation will come:x^2+5=x^2+2+m Now, x^2 will again get canceled. So, M=5 -2
=3

It can't be a level 4!!

Parth Lohomi - 6 years, 6 months ago

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