Real Algebra

Algebra Level 2

24 x 2 + 25 x 47 a x 2 = 8 x 3 53 a x 2 \frac { 24{ x }^{ 2 }+25x-47 }{ ax-2 } =-8x-3-\frac { 53 }{ ax-2 }

The equation above holds true for all values of x 2 a x \ne \dfrac 2a , where a a is a constant. What is the value of a a ?


The answer is -3.

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4 solutions

Chew-Seong Cheong
May 21, 2020

24 x 2 + 25 x 47 a x 2 = 8 x 3 53 a x 2 24 x 2 + 25 x + 6 53 a x 2 = 8 x 3 53 a x 2 24 x 2 + 25 x + 6 a x 2 53 a x 2 = 8 x 3 53 a x 2 24 x 2 + 25 x + 6 = ( 8 x 3 ) ( a x 2 ) a = 3 \begin{aligned} \frac {24x^2+25x-47}{ax-2} & = - 8x - 3 - \frac {53}{ax-2} \\ \frac {24x^2+25x+6- 53}{ax-2} & = - 8x - 3 - \frac {53}{ax-2} \\ \frac {24x^2+25x+6}{ax-2} -\frac {53}{ax-2} & = - 8x - 3 - \frac {53}{ax-2} \\ \implies 24x^2+25x+6 & = (-8x-3)(ax-2) \\ \implies a & = \boxed {-3} \end{aligned}

24 x 2 + 25 x 47 a x 2 = 8 x 3 53 a x 2 \dfrac{24x^2+25x-47}{ax-2} = -8x -3 - \dfrac{53}{ax-2}

24 x 2 + 25 x 47 = 8 x ( a x 2 ) 3 ( a x 2 ) 53 \implies 24x^2+25x-47 = -8x(ax-2) -3(ax-2) - 53

24 x 2 + 25 x 47 = 8 a x 2 + 16 x 3 a x + 6 53 \implies 24x^2+25x-47 = -8ax^2+16x -3ax +6 - 53

24 x 2 + 25 x 47 = 8 a x 2 + 16 x 3 a x 47 \implies 24x^2+25x-47 = -8ax^2+16x -3ax -47

24 x 2 + 25 x = 8 a x 2 + 16 x 3 a x \implies 24x^2+25x = -8ax^2+16x -3ax

x ( 24 x + 25 ) = x ( 8 a x + 16 3 a ) \implies x(24x+25) = x(-8ax+16-3a)

( 24 x + 25 ) = ( 8 a x + 16 3 a ) \implies (24x+25) = (-8ax+16-3a)

24 x + 9 = 8 a x 3 a = a ( 8 x + 3 ) \implies 24x+9 = -8ax-3a = -a(8x+3)

3 ( 8 x + 3 ) = a ( 8 x + 3 ) \implies 3(8x+3) = -a(8x+3)

3 = a \implies 3 = -a

a = 3 \implies a=\boxed{-3}

Great Solution

Joshua Olayanju - 1 year ago

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Thanks! Glad you like it!

Vinayak Srivastava - 1 year ago

I did the same thing. Nicely done, and well presented LaTeX! +1

Mahdi Raza - 1 year ago

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Thanks @Mahdi Raza !

Vinayak Srivastava - 1 year ago
Joshua Olayanju
May 21, 2020

There are two ways to solve this question. The faster way is to multiply each side of the given equation by ax−2 (so you can get rid of the fraction). When you multiply each side by ax−2, you should have: 24 x 2 + 25 x 47 24{ x }^{ 2 }+25x-47 ==(−8x−3)(ax−2)−53 You should then multiply (−8x−3) and (ax−2) . 24 x 2 + 25 x 47 24{ x }^{ 2 }+25x-47 =−8ax^2−3ax+16x+6−53 Then, reduce on the right side of the equation 24 x 2 + 25 x 47 24{ x }^{ 2 }+25x-47 =−8ax^2−3ax+16x−47 Since the coefficients of the x^2-term have to be equal on both sides of the equation, −8a=24, or a=−3.

Comparing coefficients of x 2 x^2 on both sides of the equation we get 8 a = 24 a = 3 -8a=24\implies a=\boxed {-3} .

Yes, correct

Joshua Olayanju - 1 year ago

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