Question

If (a-b)=7 and a^2+b^2=85,find a^3-b^3​

Answer 1

Answer:

721

Step-by-step explanation:

(a-b)=7

so

(a-b)²=7² [ squaring on both sides}

now expanding(a-b)²

a²+b²-2ab=49-----------(1)

we know a²+b²= 85---(2)

using 2 in 1

85-2ab=49

-2ab=-36

minus gets cancel both sides

2ab=36

ab=18-------3

now

a³-b³=(a-b)(a²+b²+ab)

substituting the values

a³-b³=(7)(85+18)

=721