Question

a + b = 20 , ab = 75, atunci a ( la puterea a 2-a) + b ( la puterea a 2-a ) este egal... ?

Answer 1

(a+b)=20,
(a+b)²=400
a²+2ab+b²=400
a²+b²+150=400  
a²+b²=250

Answer 2

(a + b) = 20  si ab = 75
(a + b)² = 400
a² + 2ab + b² = 400⇒a² + b²  + 2ab = 400⇒a² + b² + 2×75 = 400
⇒a²+b² =400 -150

a²+b²= 250