Basic Mathematics

Algebra Level 4

The number of Integral Value of x x for which 8 x 2 + 16 x 51 ( 2 x 3 ) ( x + 4 ) < 3 \large \frac{8x^{2}+16x-51}{(2x-3)(x+4)} < 3 is ?

1 3 2 4 5

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1 solution

Hung Woei Neoh
Jul 5, 2016

8 x 2 + 16 x 51 ( 2 x 3 ) ( x + 4 ) < 3 8 x 2 + 16 x 51 3 ( 2 x 2 + 5 x 12 ) ( 2 x 3 ) ( x + 4 ) < 0 2 x 2 + x 15 ( 2 x 3 ) ( x + 4 ) < 0 ( 2 x 5 ) ( x + 3 ) ( 2 x 3 ) ( x + 4 ) < 0 \dfrac{8x^2+16x-51}{(2x-3)(x+4)}<3\\ \dfrac{8x^2+16x-51-3(2x^2+5x-12)}{(2x-3)(x+4)}<0\\ \dfrac{2x^2+x-15}{(2x-3)(x+4)}<0\\ \dfrac{(2x-5)(x+3)}{(2x-3)(x+4)}<0

Then, draw a number line or a table to find the range of values that satisfy this inequality:

Therefore, the range is 4 < x < 3 , 3 2 < x < 5 2 -4<x<-3,\;\dfrac{3}{2}<x<\dfrac{5}{2} or ( 4 , 3 ) ( 3 2 , 5 2 ) (-4,-3)\cup\left(\dfrac{3}{2},\dfrac{5}{2}\right)

Within this range of values of x x , there is only one integer: x = 2 x=2

Therefore, the number of integral values that satisfies this inequality is 1 \boxed{1}

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