Question

(2a+3b)^2 =20 a.b=1 4a^2+9b2=

Answer 1

the answer is 8

we know that (a . b)^2 is equal to

a^2 + 2ab + b^2

`(2a + 3b) {}^(2) = 20 \\ 4a {}^(2) + 12ab + 9b {}^(2) = 20 \\ (ab = 1) \: \: \: = = > 4a {}^(2) + 9b {}^(2) = 8`

good luck