1. expand and simplify

hi this is my question:
3x^2+4+x(x-1)
for this i know i would do
3x^2+4
but after that im kinda stuck!
would i do
3x^2+4 2x-x = 3x^2+x+4??

2. $\displaystyle x(x-1) = x \cdot x + x \cdot -1 = x^2-x$

Since multiplication is higher than addition in the order of operations you need to add $\displaystyle x^2-x$ such that you get $\displaystyle 3x^2+4+(x^2-x)$

3. Originally Posted by andyboy179
hi this is my question:
3x^2+4+x(x-1)
for this i know i would do
3x^2+4
but after that im kinda stuck!
would i do
3x^2+4 2x-x = 3x^2+x+4??
Hi andyboy179,

you need to know how to multiply out the terms of x(x-1)

You do it the exact same way as 3(3-1)=3(2)=6

3(3-1)=3(3)+3(-1)=9-3=6

Or 5(5-1)=5(4)=20

5(5-1)=5(5)+5(-1)=25-5=20

You just multiply the x by both terms inside the brackets

$\displaystyle x(x-1)=x(x)+x(-1)=x^2-x$

Now combine that with $\displaystyle 3x^2+4$

Can you continue from there?

4. Originally Posted by Archie Meade
Hi andyboy179,

you need to know how to multiply out the terms of x(x-1)

You do it the exact same way as 3(3-1)=3(2)=6

3(3-1)=3(3)+3(-1)=9-3=6

Or 5(5-1)=5(4)=20

5(5-1)=5(5)+5(-1)=25-5=20

You just multiply the x by both terms inside the brackets

$\displaystyle x(x-1)=x(x)+x(-1)=x^2-x$

Now combine that with $\displaystyle 3x^2+4$

Can you continue from there?

5. Originally Posted by andyboy179
How are you getting that?

6. Originally Posted by Archie Meade
How are you getting that?
3x^2+4 x^2-x
i took away the ^2 from both because both have them
so iam left with 3x+4 x-x
3x-x= 2x
2x-x=x
then i have 4 left over so answer is x=4?

7. Originally Posted by andyboy179
3x^2+4 x^2-x
i took away the ^2 from both because both have them
so iam left with 3x+4 x-x
3x-x= 2x
2x-x=x
then i have 4 left over so answer is x=4?
You are working with some guidelines that don't apply here.

$\displaystyle 3x^2+x^2-x+4$

You find how many $\displaystyle x^2$ terms you have, how many $\displaystyle x$ terms you have and the remaining constant.

$\displaystyle 3x^2+x^2=x^2(3+1)$

8. The first line is wrong - it should state $\displaystyle 3x^2+4+(x^2-x)$. Either that or the OP is wrong.

9. so would i be 4x^+4-x?

10. Yes, it would although the convention on notation says that you use descending powers of x from left to right: $\displaystyle 4x^2-x+4$. But it's the same answer

11. okay! i think i understand now! thank you very much!!!