(5-7x)(7-7x)=0

Solution for (5-7x)(7-7x)=0 equation:

(5-7x)(7-7x)=0

We add all the numbers together, and all the variables

(-7x+5)(-7x+7)=0

We multiply parentheses ..

(+49x^2-49x-35x+35)=0

We get rid of parentheses

49x^2-49x-35x+35=0

We add all the numbers together, and all the variables

49x^2-84x+35=0

a = 49; b = -84; c = +35;
Δ = b2-4ac
Δ = -842-4·49·35
Δ = 196
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{196}=14$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-84)-14}{2*49}=\frac{70}{98}
=5/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-84)+14}{2*49}=\frac{98}{98}
=1
$