(5x+7)(x+1)=16

Solution for (5x+7)(x+1)=16 equation:

(5x+7)(x+1)=16

We move all terms to the left:

(5x+7)(x+1)-(16)=0

We multiply parentheses ..

(+5x^2+5x+7x+7)-16=0

We get rid of parentheses

5x^2+5x+7x+7-16=0

We add all the numbers together, and all the variables

5x^2+12x-9=0

a = 5; b = 12; c = -9;
Δ = b2-4ac
Δ = 122-4·5·(-9)
Δ = 324
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{324}=18$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(12)-18}{2*5}=\frac{-30}{10}
=-3
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(12)+18}{2*5}=\frac{6}{10}
=3/5
$