(5v+6)(7-v)=0

Solution for (5v+6)(7-v)=0 equation:

(5v+6)(7-v)=0

We add all the numbers together, and all the variables

(5v+6)(-1v+7)=0

We multiply parentheses ..

(-5v^2+35v-6v+42)=0

We get rid of parentheses

-5v^2+35v-6v+42=0

We add all the numbers together, and all the variables

-5v^2+29v+42=0

a = -5; b = 29; c = +42;
Δ = b2-4ac
Δ = 292-4·(-5)·42
Δ = 1681
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{1681}=41$
$v_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(29)-41}{2*-5}=\frac{-70}{-10}
=+7
$
$v_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(29)+41}{2*-5}=\frac{12}{-10}
=-1+1/5
$