1. algebra multiply

I am soo confused!
My calculus teacher told me that you cant muliply, add, subtract.. etc. one number that is squared to a number that is not
for example you cant multiply 3x^2 (4x)
I remember her saying something about a FOIL method but I missed that part of the school year. I was in a different school that didnt teach this method.
Can I do that or not?

and can I add, multiply, etc a number with an x to a number without one?
For example, would (4x)(-1+x) be 4x??

2. wait.. no that answer is wrong, itd be -4+4x^2.. right?

3. Originally Posted by KeiaBlake
wait.. no that answer is wrong, itd be -4+4x^2.. right?
nope, still wrong

it is $-4x + 4x^2$

4. 3x^2*4x = 12x^3

(4x)(-1+x) = -4x +4x^2

This is just algebra.

5. Originally Posted by paulrb
This is just algebra.

review your algebra rules, KeiaBlake. you are going to have a HARD time with any math you do if you don't know algebra

recall, $x^a \cdot x^b = x^{a + b}$

now make sure you know the other rules

6. Originally Posted by Jhevon
nope, still wrong

it is $-4x + 4x^2$
where did that second x come from?..
the problem was (4x)(-1+x)
so u multiply 4x by -1 which gives u -4x and then 4x by x which gives u 4x^2
so itd be -4x+4x^2... lol.. oh.. okay! I c! Ty!! :P

7. Originally Posted by KeiaBlake
where did that second x come from?..
the problem was (4x)(-1+x)
so u multiply 4x by -1 which gives u -4x and then 4x by x which gives u 4x^2
so itd be -4x+4x^2... lol.. oh.. okay! I c! Ty!! :P
haha, it's good to talk yourself through things sometimes

8. HELP AGAIN lol

Thats true!!
But now I really am stuck!
lol

f(g(2))
f(x)= 2x+3
g(x)=x^2-1

is it: 2(x^2-1)+3 = 2x^2-2+3 = 2x^2-1 ??
Any idea?

9. Originally Posted by KeiaBlake
Thats true!!
But now I really am stuck!
lol

f(g(2))
f(x)= 2x+3
g(x)=x^2-1

is it: 2(x^2-1)+3 = 2x^2-2+3 = 2x^2-1 ??
Any idea?
good so far! a lot of students couldn't make it to that point.

how are you stuck now? just plug in 2 for x. you have f(g(x)) and you want f(g(2)), so just plug in 2

10. Oh yeah!..
I'm so illiterate..
Guess it would have been easier to just substitute that 2 in for g(x) then plug that answer into f(x).. I just don't think far enough ahead.. lol. Thanks again!
I take it u teach this for a living?

11. Originally Posted by KeiaBlake
Oh yeah!..
I'm so illiterate..
Guess it would have been easier to just substitute that 2 in for g(x) then plug that answer into f(x).. I just don't think far enough ahead.. lol. Thanks again!
yes, i was going to say that. but i was a bit scared to. don't ask why

I take it u teach this for a living?
nope. i'm a student just like yourself.

12. this dosent seem right..

(x^2-x)(x^2-2)
is it
2x^4-2x^2-x^3+2x??
:S
If not dont tell me the answer! I wanna see if I can fix it if it's wrong.

13. no wait!! lol
is it
x^4-2x^2-x^3+2x

14. Originally Posted by KeiaBlake
this dosent seem right..

(x^2-x)(x^2-2)
is it
2x^4-2x^2-x^3+2x??
:S
If not dont tell me the answer! I wanna see if I can fix it if it's wrong.
it's wrong

15. Originally Posted by KeiaBlake
no wait!! lol
is it
x^4-2x^2-x^3+2x
haha, yup

nice catch!

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