SOLUTION: This problem is really confusing me. Can someone please help? Given f(x) = -x3 + x2 + 3x + 4, find f(-1), f(0), and f(1). Thanks.

Algebra ->  Functions -> SOLUTION: This problem is really confusing me. Can someone please help? Given f(x) = -x3 + x2 + 3x + 4, find f(-1), f(0), and f(1). Thanks.      Log On


   

Question 121965: This problem is really confusing me. Can someone please help? Given
f(x) = -x3 + x2 + 3x + 4, find f(-1), f(0), and f(1). Thanks.
Answer by HyperBrain(694) About Me  (Show Source):
You can put this solution on YOUR website!
I hope that you will understand this.., I'm trying to make you feel that it is sooo easy!

f%28x%29+=+-x%5E3+%2B+x%5E2+%2B+3x+%2B+4
f(-1)

For this, simply replace every x that you see!
f%28-1%29=-%28-1%29%5E3%2B%28-1%29%5E2%2B3%28-1%29%2B4
scratch--- %28-1%29%5E3=%28-1%29%28-1%29%28-1%29=%28%28-1%29%28-1%29%29%28-1%29=1%28-1%29=-1 thus, -%28-1%29%5E3=-%28-1%29=1
So,
f%28-1%29=1%2B%28-1%29%5E2%2B3%28-1%29%2B4
scratch----%28-1%29%5E2=%28-1%29%28-1%29=1
So,
f%28-1%29=1%2B1%2B3%28-1%29%2B4
scratch---3%28-1%29=-3
So,
f%28-1%29=1%2B1%2B%28-3%29%2B4
f%28-1%29=%281%2B1%29-3%2B4
f%28-1%29=2-3%2B4
f%28-1%29=%282-3%29%2B4
f%28-1%29=-1%2B4
f%28-1%29=3


there, that wasn't that hard.. Let's apply it ot the other ones!

f(0)

f%280%29=-0%5E3%2B0%5E2%2B3%280%29%2B4
f%280%29=-%280%29%2B0%5E2%2B3%280%29%2B4
f%280%29=0%2B0%5E2%2B3%280%29%2B4
f%280%29=0%2B0%2B3%280%29%2B4
f%280%29=0%2B0%2B0%2B4
f%280%29=%280%2B0%29%2B0%2B4
f%280%29=0%2B0%2B4
f%280%29=%280%2B0%29%2B4
f%280%29=0%2B4
f%280%29=4
what can you say? let's get it on!
f%281%29=-1%5E3%2B1%5E2%2B3%281%29%2B4
f%281%29=-%281%29%2B1%5E2%2B3%281%29%2B4
f%281%29=-1%2B1%5E2%2B3%281%29%2B4
f%281%29=-1%2B1%2B3%281%29%2B4
f%281%29=-1%2B1%2B3%2B4
f%281%29=%28-1%2B1%29%2B3%2B4
f%281%29=0%2B3%2B4
f%281%29=%280%2B3%29%2B4
f%281%29=3%2B4
f%281%29=7

That's it!

Power up,
HyperBrain!