a+b=8,a•b=15,then acube +bcube=?
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Given a + b = 8 and ab = 15.
We know that a^3 + b^3 = (a + b)(a^2 + b^2 - ab) -------- (1).
(a + b)^2 = a^2 + b^2 + 2ab
(8)^2 = a^2 + b^2 + 2 * 15
64 = a^2 + b^2 + 30
64 - 30 = a^2 + b^2
34 = a^2 + b^2 ----------------- (2)
Substitute (2) in (1), we get
a^3 + b^3 = (8) * (34 - 15)
= 8 * 19
= 152.
Therefore a^3 + b^3 = 152.
Hope this helps!
We know that a^3 + b^3 = (a + b)(a^2 + b^2 - ab) -------- (1).
(a + b)^2 = a^2 + b^2 + 2ab
(8)^2 = a^2 + b^2 + 2 * 15
64 = a^2 + b^2 + 30
64 - 30 = a^2 + b^2
34 = a^2 + b^2 ----------------- (2)
Substitute (2) in (1), we get
a^3 + b^3 = (8) * (34 - 15)
= 8 * 19
= 152.
Therefore a^3 + b^3 = 152.
Hope this helps!
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