2017 · Q33
If a + b = 5 and ab=6, then what is the value of a³+b³ ?
Elementary MathematicsAlgebra
- A35
- B40
- C90
- D125
Explanation
a³ + b³ = (a+b)³ − 3ab(a+b) = 125 − 3·6·5 = 125 − 90 = 35: option A. Option D (125) omits the −3ab(a+b) term.
If a + b = 5 and ab=6, then what is the value of a³+b³ ?
Explanation
a³ + b³ = (a+b)³ − 3ab(a+b) = 125 − 3·6·5 = 125 − 90 = 35: option A. Option D (125) omits the −3ab(a+b) term.