7(r)=3.14r2

Solution for 7(r)=3.14r2 equation:

7(r)=3.14r^2

We move all terms to the left:

7(r)-(3.14r^2)=0

We get rid of parentheses

-3.14r^2+7r=0

a = -3.14; b = 7; c = 0;
Δ = b2-4ac
Δ = 72-4·(-3.14)·0
Δ = 49
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{49}=7$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(7)-7}{2*-3.14}=\frac{-14}{-6.28}
=2+1/4.36111111111
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(7)+7}{2*-3.14}=\frac{0}{-6.28}
=0
$