28=4x(x+16)-7x

Solution for 28=4x(x+16)-7x equation:

28=4x(x+16)-7x

We move all terms to the left:

28-(4x(x+16)-7x)=0


We calculate terms in parentheses: -(4x(x+16)-7x), so:

4x(x+16)-7x

We add all the numbers together, and all the variables

-7x+4x(x+16)

We multiply parentheses

4x^2-7x+64x

We add all the numbers together, and all the variables

4x^2+57x

Back to the equation:

-(4x^2+57x)


We get rid of parentheses

-4x^2-57x+28=0

a = -4; b = -57; c = +28;
Δ = b2-4ac
Δ = -572-4·(-4)·28
Δ = 3697
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{-(-57)-\sqrt{3697}}{2*-4}=\frac{57-\sqrt{3697}}{-8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-57)+\sqrt{3697}}{2*-4}=\frac{57+\sqrt{3697}}{-8}
$