Question

Simplify $(7\sqrt{a}+5\sqrt{b})(7\sqrt{a}-5\sqrt{b})$ using multiplication and division properties of surds.

(2 marks)

Answer 1

$(7\sqrt{a}+5\sqrt{b})(7\sqrt{a}-5\sqrt{b})$
using $(a+b)(a-b)=a^2-b^2$
(1 mark)
$(7\sqrt{a}+5\sqrt{b})(7\sqrt{a}-5\sqrt{b})={\left(7\sqrt{a}\right]}^2-{\left(5\sqrt{b}\right]}^2$
$=49a-25b$
(1 mark)