Factorise completely. $$\(21 a^{2}+28 a b\)$$

E2.2.1 Manipulate directed numbers.

E2.2.2 Use brackets and extract common factors.

E2.2.3 Expand products of algebraic expressions. (e.g. expand (x + 4)(x – 7)) (Includes products of more than two brackets, e.g. (x + 4)(x – 7)(2x + 1))

E2.2.4.1 ax+bx+kay+kby

E2.2.4.2 more contents

E2.2.4.3 more contents

E2.2.4.4 more contents