# Thread: need help with algebra (long division)

1. ## need help with algebra (long division)

Hey i was wondering if anyone could help me?

im doing some summer revision on algebra and i got stuck on this long division algebra question :

(x ³ + 11x - 30) ÷ (x-2)

i keep getting the answer: x ² + 9x + 36

the correct answer is : x ² + 2x + 15

i would really appreciate if anyone could help me out with this, i know it seems like a very easy question for most people but maths is my worst subject

2. Hi

Maybe your mistake comes from the fact that there is no x²-term in x ³ + 11x - 30

3. thanks for replying !!! though (x ³ + 11x - 30) is the question, not the answer,

im wondering how to get the answer : x ² + 2x + 15
from the question (x ³ + 11x - 30) divided by (x-2)

as i am getting the same wrong answer from my numerous attempts to try solve it lol. i know that i have to add the missing factor ie.
0x

(x ³ + 11x + 0 x - 30) yet to no avail can i get the right answer

4. Hello, cliste09!

$\displaystyle (x^3 + 11x - 30) \div (x-2)$

i keep getting the answer: .$\displaystyle x^2 + 9x + 36$ .
How?
I can guess how you got a "9" . . . but the "36"?

. . $\displaystyle \begin{array}{ccccccccc}&&&& x^2 &+&2x&-&15 \\ &&---&---&---&---&---&---&--- \\ x-2&|&x^3 &&&+&11x &-&30 \\ &&x^3&-&2x^2 \\ &&---&---&--- \\ &&&&2x^2&+&11x \\ &&&&2x^2&-&4x \\ &&&&---&---&--- \\ &&&&&&15x&-&30 \\ &&&&&&15x&-&30 \\ &&&&&&---&---&--- \end{array}$

5. Originally Posted by cliste09
thanks for replying !!! though (x ³ + 11x - 30) is the question, not the answer,

im wondering how to get the answer : x ² + 2x + 15
from the question (x ³ + 11x - 30) divided by (x-2)

as i am getting the same wrong answer from my numerous attempts to try solve it lol. i know that i have to add the missing factor ie.
0x

(x ³ + 11x + 0 x - 30) yet to no avail can i get the right answer
Running gag told you what the problem was: You need to write $\displaystyle x^3+ 11x- 30$ as $\displaystyle x^3+ 0x^2+ 11x- 30$ in order that you keep things lined up correctly. Notice that Soroban did not actually write "$\displaystyle 0x^2$" but he did leave a space for it. I prefer to write $\displaystyle 0x^2$ so as not to confuse myself! Soroban is clearly more adept at this than you or I.

6. thank you so much!!! you're a life-saver lol i was about to give up on it even though its not even an exam question , ahh i see where i went wrong!!!

haha as for the 36 i got that when i did this:

x ² + 9x -36
--------------------
x-2 { x ³ + 11x + 0x - 30} step 1= x ³ div. by x = x ²
x ³ - 2x ² + 0x step 2= x ² mul. by x-2= x ³
------------------
9x² + 0x step 3= 9x² div. by x²=9x
9x² - 18x step 4= 9x(x-2)=9x²-18
------------------
- 18x -30 step 5=cancel 9x²,bring down -18x and -30
- 18x-36 now -18x div. by x= 18

step 6= -18(x-2)=-18x + 36 ( by mistake i
must of just put 36 as the last term on
top)