Question

If a+b = 8 ,a square + b square = 40 find a cube + b cube

Answer 1

hello...


a3 + b3 = (a + b)(a2 + b2 - ab)
= (8)(40 - ab)  
(a + b)2  (a+b)2 = a2 + b2 + 2ab
(8)2 = 40 + 2ab64 - 40
= 2ab24/2
= abab = 12...(1)
Therefore,a3 +b3 = (8)(40 - 12) ....(from 1)
(8)(28)224.

thank you ☺

Answer 2

a3 + b3 = (a + b)(a2 + b2 - ab)
= (8)(40 - ab)
To find the value of ab we can find it using the formula of (a + b)2
(a+b)2 = a2 + b2 + 2ab
(8)2 = 40 + 2ab
64 - 40 = 2ab
24/2 = ab
ab = 12...(1)
Therefore,
a3 +b3 = (8)(40 - 12) .....(from 1)
(8)(28)
224.​
Hope u found this answer helpful..