Question

If a-b=7 and a square + b square = 85, then find the value of a cube - b cube​

Answer 1

Answer:

the answer is 721

Step-by-step explanation:

a - b = 7 ...given equation 1......

( a - b)² = a² + b² - 2ab

49 = 85 - 2ab

the value of a² + b² is 85 given

by here the value of 2ab is 36

now ( a + b) ² = a² + b² + 2ab

= 85 + 36

( a + b)² = 121

a + b = 11 equation 2.......

now add equation for 1 and 2, I we get

a = 9

b = 2

now the value of a³- b³

= 9³ - 2³

= 721 ans