(-7c+5)(-4c+7)=0

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

(-7c+5)(-4c+7)=0

We multiply parentheses ..

(+28c^2-49c-20c+35)=0

We get rid of parentheses

28c^2-49c-20c+35=0

We add all the numbers together, and all the variables

28c^2-69c+35=0

a = 28; b = -69; c = +35;
Δ = b2-4ac
Δ = -692-4·28·35
Δ = 841
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{841}=29$
$c_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-69)-29}{2*28}=\frac{40}{56}
=5/7
$
$c_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-69)+29}{2*28}=\frac{98}{56}
=1+3/4
$