if a+b=10,ab=21,find a3+b3
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Answered by
8
(a+b)² = a²+b²+2ab
10² = a²+b²+2(21)
100 = a²+b²+42
100-42 = a²+b²
58 = a²+b²
we know that,
a³+b³ = (a+b)(a²+b²-ab)
a³+b³ = (10)(58-21)
a³+b³ =10 × 37 = 370
hope this helps
10² = a²+b²+2(21)
100 = a²+b²+42
100-42 = a²+b²
58 = a²+b²
we know that,
a³+b³ = (a+b)(a²+b²-ab)
a³+b³ = (10)(58-21)
a³+b³ =10 × 37 = 370
hope this helps
Answered by
1
Hi !
a + b = 10
ab = 21
a³ + b³ = (a+b)³ + 3ab(a+b)
= 10³ + 3 x 21 (10)
= 1000 + 630
= 1630
a³ + b³ = 1630
a + b = 10
ab = 21
a³ + b³ = (a+b)³ + 3ab(a+b)
= 10³ + 3 x 21 (10)
= 1000 + 630
= 1630
a³ + b³ = 1630
Anonymous:
it will be -3ab(a+b) not what u did .
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