Begginer Question: Replacing variables with number.

[Chris.]

If i enter Simplify((X^2-7x)(8-x^3))
Calculator returns "-x^5+7x^4+8x^2-56x"
How would I tel the calculator to replace all values of x with a number for example -1

I tried Solve(-x^5+7x^4+8x^2-56x,x=-1)
And it returned the wrong answer.

[Didier Lachieze]

You can use subst: subst(-x^5+7*x^4+8*x^2-56*x,x=-1)
or define a function: f(x):=(x^2-7*x)*(8-x^3) and then enter f(-1)

[Joe Horn]

Another way: Use the WHERE symbol (looks like "|"; it's the 3rd item in the template box). Your example would be -x^5+7*x^4+8*x^2-56*x|x=-1.