Sorry I got he answer, the first bracket should be (1-x)^2 and not (1-x^2), the latter is a difference of two squares, hence the error when factorising and simplying.View attachment 21794
I cant work out whats wrong, I cant get the solution required as my first derivative is different by a minus sign.
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I see. Thats a good point.It is a very bad idea to use "x" to indicate multiplication when you are using "x" as the variable (and even when the variable isn't x)! I spent some time trying to figure out why you had "x- 1" in the first expression!