Find the value of the following expressions at a = 1 and b = –2:(i)

1.	Find the value of the following expressions at a = 1 and b = –2:(i) a2 + b2 + 3ab (ii) a3 + a2b + ab2 + b3
Answer» (i) Value of a² + b² + 3ab at a = 1 and b = – 2 = (1)² + (–2)² + 3 (1)(–2) = 1 + 4 – 6 = 5 – 6 = – 1 (ii) Value of a³ + a²b + ab² + b³ at a = 1 and b = – 2 = (1)³ + (1)²(–2)+(1) (–2)² + (–2)³ = 1 – 2 + 4 – 8 = 5 – 10 = – 5

Find the value of the following expressions at a = 1 and b = –2:(i) a2 + b2 + 3ab (ii) a3 + a2b + ab2 + b3

Answer»

(i) Value of a² + b² + 3ab at a = 1 and b = – 2

= (1)² + (–2)² + 3 (1)(–2)

= 1 + 4 – 6

= 5 – 6

= – 1

(ii) Value of a³ + a²b + ab² + b³ at a = 1 and b = – 2

= (1)³ + (1)²(–2)+(1) (–2)² + (–2)³

= 1 – 2 + 4 – 8

= 5 – 10

= – 5