CDS 2022 · PYQ · Algebra · medium
If a+b = 2 and 1/a + 1/b = 2, then what is the value of a³+b³?
Answer
The correct answer is C: 2. 1/a+1/b = (a+b)/(ab) = 2/ab = 2, so ab = 1. a³+b³ = (a+b)³-3ab(a+b) = 8 - 3·1·2 = 2.
- A.4
- B.8
- C.2✓ Correct
- D.6
1/a+1/b = (a+b)/(ab) = 2/ab = 2, so ab = 1. a³+b³ = (a+b)³-3ab(a+b) = 8 - 3·1·2 = 2.
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