Question

if y-1/y=9 find the value of y^3-1/y^3​

Answer 1

Step-by-step explanation:

I assume the question is y - (1/y) = 3 instead of (y-1)/y = 6 and we have to find y^3 - (1/y^3) not (y^3–1)/y^3

So with these assumptions I move ahead.

We know that (a-b)^3 = a^3 - b^3 -3*a*b(a-b)

Now y - (1/y) = 6

On cubing both sides we get

(y -(1/y) )^3 = 6^3 = 216

=> y^3 - (1/y)^3 - 3*y*(1/y)*(y - (1/y) ) = 216

=> y^3 - 1/(y)^3 - 3(y - (1/y) ) = 216

=> y^3 - 1/y^3 - 3* 6 = 216 [ because y -(1/y) = 6]

=> y^3 - 1/y^3 = 216 + 18 = 234

Aswers by .....................anushka❤