Question

8x (x-1)=ø

Answer 1

you have something against the digit 0? Why drag in the Greek letter phi?

Assuming you want to find vales of x which make the equation true, you have three choices:

8=0
x = 0
x-1 = 0

I guess you can find the needed x values now, right?

The reason we always set the product on the left equal to zero is that if a product of factors is zero, at least one of the factors must be zero.