(7x+21)*(7x+21)=175

Solution for (7x+21)*(7x+21)=175 equation:

(7x+21)(7x+21)=175

We move all terms to the left:

(7x+21)(7x+21)-(175)=0

We multiply parentheses ..

(+49x^2+147x+147x+441)-175=0

We get rid of parentheses

49x^2+147x+147x+441-175=0

We add all the numbers together, and all the variables

49x^2+294x+266=0

a = 49; b = 294; c = +266;
Δ = b2-4ac
Δ = 2942-4·49·266
Δ = 34300
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{34300}=\sqrt{4900*7}=\sqrt{4900}*\sqrt{7}=70\sqrt{7}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(294)-70\sqrt{7}}{2*49}=\frac{-294-70\sqrt{7}}{98}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(294)+70\sqrt{7}}{2*49}=\frac{-294+70\sqrt{7}}{98}
$