68=140x-16x^2

Solution for 68=140x-16x^2 equation:

68=140x-16x^2

We move all terms to the left:

68-(140x-16x^2)=0

We get rid of parentheses

16x^2-140x+68=0

a = 16; b = -140; c = +68;
Δ = b2-4ac
Δ = -1402-4·16·68
Δ = 15248
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:

$\sqrt{\Delta}=\sqrt{15248}=\sqrt{16*953}=\sqrt{16}*\sqrt{953}=4\sqrt{953}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-140)-4\sqrt{953}}{2*16}=\frac{140-4\sqrt{953}}{32}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-140)+4\sqrt{953}}{2*16}=\frac{140+4\sqrt{953}}{32}
$