(8x-7)(9x+9)=0

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Solution for (8x-7)(9x+9)=0 equation:



(8x-7)(9x+9)=0
We multiply parentheses ..
(+72x^2+72x-63x-63)=0
We get rid of parentheses
72x^2+72x-63x-63=0
We add all the numbers together, and all the variables
72x^2+9x-63=0
a = 72; b = 9; c = -63;
Δ = b2-4ac
Δ = 92-4·72·(-63)
Δ = 18225
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{18225}=135$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(9)-135}{2*72}=\frac{-144}{144} =-1 $
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(9)+135}{2*72}=\frac{126}{144} =7/8 $

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