7r^2-40r-63=0

Solution for 7r^2-40r-63=0 equation:

7r^2-40r-63=0

a = 7; b = -40; c = -63;
Δ = b2-4ac
Δ = -402-4·7·(-63)
Δ = 3364
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{3364}=58$
$r_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-40)-58}{2*7}=\frac{-18}{14}
=-1+2/7
$
$r_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-40)+58}{2*7}=\frac{98}{14}
=7
$