Math, asked by shristisingh31, 1 year ago

a minus b equals to 7 a square + b square = 85 find a cube minus b cube

Answers

Answered by bhatiamona
1

Answer:

a³-b³= 721

Step-by-step explanation:

Here given information is  a-b=7 and a²+b²=85

We concludes,

a= b-7.....................(1)

a²+b²=85.........................(2)

Putting the value of a in equation (2)

(b-7)²+b²= 85

b²+49+14b+b²=85

2b²+14b-36=0

b²+7b-18=0

b²+9b-2b-18=0

b(b+9)-2(b+9)=0

(b-2)(b-9)=0

b=2

and a=9

The value of a=9 and b=2

As we know,

a³-b³=(a-b)(a²+ab+b²)

Putting the values of equation (1) & (2)

=7(85+9x2)

=721

Therefore, a³-b³= 721

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