Question

a2+b2+8a+6b+25=0,a3+b3=????

Answer 1

2a+2b+8a+6b+25 = 0
10a+8b+25 = 0
multipling by 3
30a+24b+75 = 0 --------eq.1
Now
3a+3b = 0 ----------eq3
multipling by 10
30a+30b = 0 -----------eq.2

subtrcting eq2 from eq1
30a+24b+75-30a-30b = 0
-6b = -75
b = 25/2

using eq3
3a+3(25/2) = 0
a = -25/2