Question

If a + b = 7 and ab= 3, then what is the value of a³+b³?

Answer 1

Correct option is
A
28
Given,
a+b=7 and ab=15
Squaring both sides,we get,
(a+b)
2
=7
2

=a
2
+b
2
+2ab=49 [since(a+b)
2
=a
2
+b
2
+2ab]
=a
2
+b
2
+2(15)=49
=a
2
+b
2
=49−30
=a
2
+b
2
=19
Now,
(a
3
+b
3
)
=(a+b)(a
2
+b
2
−ab)
=7(19−15)
=7(4)
=28
verified_toppr
Answer verified by Toppr

Answer 2

Answer:

a3+b3

now,

a+b=7 and ab=3

a3+b3

73×33

91x18

1618

therefore,the answer is 1618