Question

Find the value of 2a2
– 3ab3
– b
3
+ 5ab – 4a2
b if a = -1 b = 2

Answer 1

$= 2 {a}^{2} - 3a {b}^{3} - {b}^{3} + 5ab - 4 {a}^{2} b$

$= 2 {( - 1)}^{2} - 3( - 1) {(2)}^{3} - {(2)}^{3} \\ + 5( - 1)(2) - 4 {( - 1)}^{2} (2)$

$= 2(2) - 3( - 8) - 8 + 5( - 2) + 4( - 2)$

$= 4 + 24 - 8 - 10 - 8$

$= 28 - 26$

$= 2$