Question

(a) If x + y = 1, x3 + y3 = 4, then x2 + y2 = ..

Answer 1

hence x2+y2= 3 if u didn't get feel free to ask

Answer 2

x³ + y³ = (x+y)(x² - xy + y²) 
So substitute the values to get 
x² + y² - xy = 4    ---(1)
(x+y)² - 3 xy = 4
So 1 - 3xy = 4
 xy = -1

using (1)  x² + y² = 3