Question:
Find each of the following products:
(i) (4a + 5b) × (5a − 6b)
(ii) (6x2 − x + 8) × (x2 − 3)
Solution:
(i) $(4 a+5 b) \times(5 a-6 b)$
$=20 a^{2}-24 a b+25 a b-30 b^{2}$
$=20 a^{2}+a b-30 b^{2}$
(ii) (6x2 − x + 8) × (x2 − 3)
$=6 x^{4}-18 x^{2}-x^{3}+3 x+8 x^{2}-24$
$=6 x^{4}-x^{3}-18 x^{2}+8 x^{2}+3 x-24$
$=6 x^{4}-x^{3}-10 x^{2}+3 x-24$