Solve x^2+90^2=(x+30)^2

$$x ^ { 2 } + 90 ^ { 2 } = ( x + 30 ) ^ { 2 }$$

Solve for x

$$x=120$$

Steps for Solving Linear Equation

Calculate 90 to the power of 2 and get 8100.

$$x^{2}+8100=\left(x+30\right)^{2}$$

Use binomial theorem \left(a+b\right)^{2}=a^{2}+2ab+b^{2} to expand \left(x+30\right)^{2}.

$$x^{2}+8100=x^{2}+60x+900$$

Subtract x^{2} from both sides.

$$x^{2}+8100-x^{2}=60x+900$$

Combine x^{2} and -x^{2} to get 0.

$$8100=60x+900$$

Swap sides so that all variable terms are on the left hand side.

$$60x+900=8100$$

Subtract 900 from both sides.

$$60x=8100-900$$

Subtract 900 from 8100 to get 7200.

$$60x=7200$$

Divide both sides by 60.

$$x=\frac{7200}{60}$$

Divide 7200 by 60 to get 120.

$$x=120$$