a+b=4 a3+b3=28 find a3+b3
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1
28 is answer already given in question
Answered by
0
Answer:
-3
Step-by-step explanation:
We have:
a^3a
3
+ b^3b
3
= 28 and a + b = 4
We have to find, the value of ab = ?
Solution:
a + b = 4
Cubing both sides, we get
∴ (a + b)^3(a+b)
3
= 4^34
3
Using the algebraic identity,
(a + b)^3(a+b)
3
= a^3a
3
+ b^3b
3
+ 3ab(a + b)
⇒ a^3a
3
+ b^3b
3
+ 3ab(a + b) = 64
Put a^3a
3
+ b^3b
3
= 28 and a + b = 4, we get
⇒ 28 + 3ab(4) = 64
⇒ 12ab = 64 - 28 = 36
⇒ ab = \dfrac{36}{12}
12
36
⇒ ab = 3
Thus, the value of ab is "equal to 3".
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