(5x2-32x)-21=0

Solution for (5x2-32x)-21=0 equation:

(5x^2-32x)-21=0

We get rid of parentheses

5x^2-32x-21=0

a = 5; b = -32; c = -21;
Δ = b2-4ac
Δ = -322-4·5·(-21)
Δ = 1444
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1444}=38$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-32)-38}{2*5}=\frac{-6}{10}
=-3/5
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-32)+38}{2*5}=\frac{70}{10}
=7
$