(7x+9)(7x+9)=64

Solution for (7x+9)(7x+9)=64 equation:

(7x+9)(7x+9)=64

We move all terms to the left:

(7x+9)(7x+9)-(64)=0

We multiply parentheses ..

(+49x^2+63x+63x+81)-64=0

We get rid of parentheses

49x^2+63x+63x+81-64=0

We add all the numbers together, and all the variables

49x^2+126x+17=0

a = 49; b = 126; c = +17;
Δ = b2-4ac
Δ = 1262-4·49·17
Δ = 12544
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$\sqrt{\Delta}=\sqrt{12544}=112$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(126)-112}{2*49}=\frac{-238}{98}
=-2+3/7
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(126)+112}{2*49}=\frac{-14}{98}
=-1/7
$