(7x-20)(4x)=10

Solution for (7x-20)(4x)=10 equation:

(7x-20)(4x)=10

We move all terms to the left:

(7x-20)(4x)-(10)=0

We multiply parentheses

28x^2-80x-10=0

a = 28; b = -80; c = -10;
Δ = b2-4ac
Δ = -802-4·28·(-10)
Δ = 7520
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:

$\sqrt{\Delta}=\sqrt{7520}=\sqrt{16*470}=\sqrt{16}*\sqrt{470}=4\sqrt{470}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-80)-4\sqrt{470}}{2*28}=\frac{80-4\sqrt{470}}{56}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-80)+4\sqrt{470}}{2*28}=\frac{80+4\sqrt{470}}{56}
$