25=3x-5x(4-2x)

Solution for 25=3x-5x(4-2x) equation:

25=3x-5x(4-2x)

We move all terms to the left:

25-(3x-5x(4-2x))=0

We add all the numbers together, and all the variables

-(3x-5x(-2x+4))+25=0


We calculate terms in parentheses: -(3x-5x(-2x+4)), so:

3x-5x(-2x+4)

We multiply parentheses

10x^2+3x-20x

We add all the numbers together, and all the variables

10x^2-17x

Back to the equation:

-(10x^2-17x)


We get rid of parentheses

-10x^2+17x+25=0

a = -10; b = 17; c = +25;
Δ = b2-4ac
Δ = 172-4·(-10)·25
Δ = 1289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(17)-\sqrt{1289}}{2*-10}=\frac{-17-\sqrt{1289}}{-20}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(17)+\sqrt{1289}}{2*-10}=\frac{-17+\sqrt{1289}}{-20}
$