9k(7k+5)=0

Solution for 9k(7k+5)=0 equation:

9k(7k+5)=0

We multiply parentheses

63k^2+45k=0

a = 63; b = 45; c = 0;
Δ = b2-4ac
Δ = 452-4·63·0
Δ = 2025
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{2025}=45$
$k_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(45)-45}{2*63}=\frac{-90}{126}
=-5/7
$
$k_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(45)+45}{2*63}=\frac{0}{126}
=0
$