a-x=1

Question

b+1=x
ab=?

a. x^2-1
b. x^2
c. (x+1)^2
d. (x-1)^2
e. X^2+1

I don't know how to do it, any body can answer this question and step by step tell me how to do it, thank you

Answer 1

rearrange things a bit and you have

a = x+1
b = x-1

so,
ab = (x+1)(x-1) = x^2-1