(7s+5)(4s+9)=0

Solution for (7s+5)(4s+9)=0 equation:

(7s+5)(4s+9)=0

We multiply parentheses ..

(+28s^2+63s+20s+45)=0

We get rid of parentheses

28s^2+63s+20s+45=0

We add all the numbers together, and all the variables

28s^2+83s+45=0

a = 28; b = 83; c = +45;
Δ = b2-4ac
Δ = 832-4·28·45
Δ = 1849
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$s_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$s_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1849}=43$
$s_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(83)-43}{2*28}=\frac{-126}{56}
=-2+1/4
$
$s_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(83)+43}{2*28}=\frac{-40}{56}
=-5/7
$