Question

Please help me. How do you do this.

Answer 1

Use the Pythagorean theorem:

`x^2+4^2=10^2`

`x^2+16=100` subtract 16 from both sides

`x^2=84\to x=√(84)\\\\x=√(4\cdot21)\\\\x=\sqrt4\cdot√(21)\\\\\boxed{2√(21)}`