28a-11a=-a^2

Solution for 28a-11a=-a^2 equation:

28a-11a=-a^2

We move all terms to the left:

28a-11a-(-a^2)=0

We add all the numbers together, and all the variables

-(-a^2)+17a=0

We get rid of parentheses

a^2+17a=0

a = 1; b = 17; c = 0;
Δ = b2-4ac
Δ = 172-4·1·0
Δ = 289
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{289}=17$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(17)-17}{2*1}=\frac{-34}{2}
=-17
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(17)+17}{2*1}=\frac{0}{2}
=0
$