(7a+4)(5a-2)=0

Solution for (7a+4)(5a-2)=0 equation:

(7a+4)(5a-2)=0

We multiply parentheses ..

(+35a^2-14a+20a-8)=0

We get rid of parentheses

35a^2-14a+20a-8=0

We add all the numbers together, and all the variables

35a^2+6a-8=0

a = 35; b = 6; c = -8;
Δ = b2-4ac
Δ = 62-4·35·(-8)
Δ = 1156
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1156}=34$
$a_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(6)-34}{2*35}=\frac{-40}{70}
=-4/7
$
$a_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(6)+34}{2*35}=\frac{28}{70}
=2/5
$