Begginer Question: Replacing variables with number.
03-17-2017, 10:22 PM (This post was last modified: 03-17-2017 11:38 PM by Chris..)
Post: #1
 Chris. Junior Member Posts: 6 Joined: Mar 2017
Begginer Question: Replacing variables with number.
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.
03-18-2017, 12:00 AM
Post: #2
 Didier Lachieze Senior Member Posts: 1,449 Joined: Dec 2013
RE: Begginer Question: Replacing variables with number.
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)
03-18-2017, 04:04 AM
Post: #3 Joe Horn Senior Member Posts: 1,841 Joined: Dec 2013
RE: Begginer Question: Replacing variables with number.
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.

<0|ɸ|0>
-Joe-
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