Question

if a+2b = 3 and ab = -5, then find the value of:

(i) a²+4b²
(ii) a³+8b³

please explain​

Answer 1

Answer:

a+2b=3

we know that (a+b)^2 = a^2+2ab+b^2

a^2+(2b)^2+2a*2b=3^2

a^2+4b^2-20=9 [ given that ab=-5]

a^2+4b^2 =20+9

a^2+4b^2=29