280=4x^2+7x

Solution for 280=4x^2+7x equation:

280=4x^2+7x

We move all terms to the left:

280-(4x^2+7x)=0

We get rid of parentheses

-4x^2-7x+280=0

a = -4; b = -7; c = +280;
Δ = b2-4ac
Δ = -72-4·(-4)·280
Δ = 4529
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-7)-\sqrt{4529}}{2*-4}=\frac{7-\sqrt{4529}}{-8}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-7)+\sqrt{4529}}{2*-4}=\frac{7+\sqrt{4529}}{-8}
$