Question

6. If a + b2 = 58 and ab = 21, find the value of:
(a) atb
(b) a-b​

Answer 1

A+b=10

cubing both the sides

(A+b)3= A3+b3+3ab(a+b)=1000

A2+b2=58

(a+b)=10

sqauring both the sides

A2+b2+2ab=100

58+2ab=100

2ab=42

ab=21

(A+b)3= A3+b3+3ab(a+b)

A3+b3+3(21)(10)=1000

A3+b3=1000-630

A3+b3=370

answer is 370