25=2(x-4)(x+7)

Solution for 25=2(x-4)(x+7) equation:

25=2(x-4)(x+7)

We move all terms to the left:

25-(2(x-4)(x+7))=0

We multiply parentheses ..

-(2(+x^2+7x-4x-28))+25=0


We calculate terms in parentheses: -(2(+x^2+7x-4x-28)), so:

2(+x^2+7x-4x-28)

We multiply parentheses

2x^2+14x-8x-56

We add all the numbers together, and all the variables

2x^2+6x-56

Back to the equation:

-(2x^2+6x-56)


We get rid of parentheses

-2x^2-6x+56+25=0

We add all the numbers together, and all the variables

-2x^2-6x+81=0

a = -2; b = -6; c = +81;
Δ = b2-4ac
Δ = -62-4·(-2)·81
Δ = 684
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{684}=\sqrt{36*19}=\sqrt{36}*\sqrt{19}=6\sqrt{19}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-6)-6\sqrt{19}}{2*-2}=\frac{6-6\sqrt{19}}{-4}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-6)+6\sqrt{19}}{2*-2}=\frac{6+6\sqrt{19}}{-4}
$