Question

Factorise: 84 2r 2r2

Answer 1

84 2r 2r2= $-2(r^2 + r - 42)$

= $-2(r^2 + 7r - 6r - 42)$

= $-2[r(r + 7) - 6(r + 7)]$

= $-2(r - 6)(r + 7)$

= $2(6 - r)(r + 7)$