Question

if a +b=12, a²+b²=90.find a³+b³​

Answer 1

Answer:

(a+b)=12

(a+b)²=a²+b²+2ab

substitute the values

(12)²=90+2ab

24=90+2ab

24-90=2ab

-66/2=ab

-33=ab.......(1)

a²+b²=90

a²+b²-2ab=90-2ab

(a-b)²=90-(-66).... from (1)

(a-b)²=90+66

(a-b)²=156

a-b=12.4

a³+b³=(a-b)(a²+ab+b²)........ formula

a³+b³=12.48(90-33)

=12.48(57)

=711.36

~711

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