10a(4a+7)=0

Solution for 10a(4a+7)=0 equation:

10a(4a+7)=0

We multiply parentheses

40a^2+70a=0

a = 40; b = 70; c = 0;
Δ = b2-4ac
Δ = 702-4·40·0
Δ = 4900
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{4900}=70$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(70)-70}{2*40}=\frac{-140}{80}
=-1+3/4
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(70)+70}{2*40}=\frac{0}{80}
=0
$