(-4*x)x-15=-64

Solution for (-4*x)x-15=-64 equation:

(-4*x)x-15=-64

We move all terms to the left:

(-4*x)x-15-(-64)=0

We add all the numbers together, and all the variables

(-4x)x-15-(-64)=0

We add all the numbers together, and all the variables

(-4x)x+49=0

We multiply parentheses

-4x^2+49=0

a = -4; b = 0; c = +49;
Δ = b2-4ac
Δ = 02-4·(-4)·49
Δ = 784
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{784}=28$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(0)-28}{2*-4}=\frac{-28}{-8}
=3+1/2
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(0)+28}{2*-4}=\frac{28}{-8}
=-3+1/2
$