Question

Which expression is equal to...?

Answer 1

- √7

using the ' law of radicals '

√a × √b ⇔ √ab

simplifying each radical

√28 = √(4 × 7) = √4 × √7 = 2√7

√63 = √(9 × 7) = √9 × √7 = 3√7

7√28 - 5√63 = 7(2√7) - 5(3√7) = 14√7 - 15√7 = - √7