Thread: 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??

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

Originally Posted by KeiaBlake

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

nope, still wrong

it is

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

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

This is just algebra.

Originally Posted by paulrb

This is just algebra.

glad to hear that!

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,

now make sure you know the other rules

Originally Posted by Jhevon

nope, still wrong

it is

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

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

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?

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

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?

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.

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.

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

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

Originally Posted by KeiaBlake

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

haha, yup

nice catch!