if a minus b = 7 then a square + b square equal 85 find a cube minus b cube and a cube plus b cube
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a-b=7
a2+b2=85
Use the identity a3−b3=(a−b)(a2+ab+b2)
and
(a-b)square=a square+b square-2ab
(7)square=85-2ab
2ab=85-49
2ab=36
ab=36÷2=18
a cube-b cube=7(85+18)
=7×103
=721
a2+b2=85
Use the identity a3−b3=(a−b)(a2+ab+b2)
and
(a-b)square=a square+b square-2ab
(7)square=85-2ab
2ab=85-49
2ab=36
ab=36÷2=18
a cube-b cube=7(85+18)
=7×103
=721
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