Question

Use the formula to expand:

(8) (4l – 2m – 3n)²

Answer 1

We know that (a + b + c)² = a² + b² + c² + 2ab + 2bc + 2ac.
Comparing (4l – 2m – 3n)² with (a + b + c)² , we get:
a = 4l, b = –2m and c = –3n
Substituting these in the above formula:
(4l – 2m – 3n)² = (4l)² + (–2m)² + (–3n)² + 2 × (4l) × (–2m) +2× (–2m)×(–3n) + 2 × (–3n) × (4l)
= 16l² + 4m² + 9n² – 16lm + 12mn – 24ln