Question

If a+2b = 3 and ab =-5 then find the value of a^2 + 4b^2

Answer 1

Step-by-step explanation:

a + 2b = 3

ab = -5

a = 3 - 2b

$b = \frac{3 - a}{2}$

$ab = (3 - 2b) \frac{3 - a}{2} = - 5$

$(3 - 2b)(3 - a) = - 10$

3 - 2b = -10 ; 3 - a = -10

b = 13/2 ; a = 13

${a}^{2} + 4 {b}^{2} = 126 + 126 = 252$