Question

(a-b)=3 and ab=5 then a3-b3=

Answer 1

Answer:

(a-b)³=a³-b³-3ab(a-b)

now substitute the given value in the equation

(3)³=a³-b³-3.5.(3)

27=a³-b³-45

a³-b³= 27+45

a³-b³= 72

Answer 2

Answer:

(a-b)=3

cubing both sides

(a-b)^3=(3)^3

(a-b)(a^2+b^2-2ab)=9

(a-b)(a^2+b^2-2*5)=9

(a-b)(a^2+b^2-10)=9

a^3+ab^2-10a-a^2b-b^3+10b=9

a^3-b^3-10 (a-b)+ab^2-a^2b=9

a^3-b^3-10*3-a^2b+ab^2=9

a^3-b^3-30-ab (a-b)=9

a^3-b^3-30-5*3=9

a^3-b^3-30-15=9

a^3-b^3-45=9

a^3-b^3=9+45

a^3-b^3=54.

Hope it will help you.