Question

Use the formula to multiply:
(11) (9 – p) (9 – p)

Answer 1

As (x + a) (x + b) = x² + (a + b)x + ab
So, (9 – p) (9 – p) = (–p + 9) (–p + 9)
= (–p)² + (9 + 9) (–p) + 9 × 9
= p² – 18p + 81

∴ (9 – p) (9 – p) = p² – 18p + 81