Question

Find the value of x.

Answer 1

`\huge\boxed{x=√(21)}`

Explanation:

ΔABD and ΔBCD are similar (AAA).

Therefore the corresponding sides are in proportion:

`(BD)/(CD)=(AD)/(BD)`

Substitute

`BD=x;\ CD=3;\ AD=7`

`(x)/(3)=(7)/(x)` cross multiply

`(x)(x)=(3)(7)\\\\x^2=21\to x=√(21)`