2x(8-7x)=-11

Solution for 2x(8-7x)=-11 equation:

2x(8-7x)=-11

We move all terms to the left:

2x(8-7x)-(-11)=0

We add all the numbers together, and all the variables

2x(-7x+8)-(-11)=0

We add all the numbers together, and all the variables

2x(-7x+8)+11=0

We multiply parentheses

-14x^2+16x+11=0

a = -14; b = 16; c = +11;
Δ = b2-4ac
Δ = 162-4·(-14)·11
Δ = 872
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:

$\sqrt{\Delta}=\sqrt{872}=\sqrt{4*218}=\sqrt{4}*\sqrt{218}=2\sqrt{218}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(16)-2\sqrt{218}}{2*-14}=\frac{-16-2\sqrt{218}}{-28}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(16)+2\sqrt{218}}{2*-14}=\frac{-16+2\sqrt{218}}{-28}
$