Question

If a - b = 7 and
${a}^{2}$
+
${b}^{2}$
= 85 then find the value of
${a}^{3}$
-
${b}^{3}$
​

Answer 1

Answer:

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

7^2 = 85-2ab

49+85 = 2ab

134 = 2ab

ab = 67

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

= 7 * (85+67)

= 7*152

= 1064