Question

If 3x + 4y = 40 and xy = 5, find the value of 27x3 + 64y3

we have the solution but how did 12xy become 36xy?​

Answer 1

Answer:

By identity.

Step-by-step explanation:

I don't know you are in which class but there is an identity

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

Actually its a modified result of (a + b)^2 identity.

If we expand this identity it becomes

a^2 + b^2 + 2ab

If we subtract 2ab from this we get a^2 + b^2.

This result is used to solve this question.

I hope your confusion is clear.