factor by grouping:
2x^3+36-8x^2-9x

Question

factor by grouping: 
2x^3+36-8x^2-9x

mathstudent55 · Answer

First, rewrite the polynomial in descending order of degree.

mathstudent55 · Answer

Can you rewrite the polynomial in descending order of the exponent of x and show it?

anonymous · Answer

2x^3-8x^2-9x+36?

mathstudent55 · Answer

Great.
Now group the first two terms together, and group the second two terms together.
Be careful with the sign of the second group.

anonymous · Answer

i got (x-4)(2x^2-4) but i don'
t think its right...

mathstudent55 · Answer

$\large (2x^3 - 8x^2) - 9x + 36$

When you put parentheses around the second group, you need to adjust the sign inside.

$\large (2x^3-8x^2)-(9x-36)$

mathstudent55 · Answer

Now you factor out a common factor out of the first group, and do the same for the second group.

$\large 2x^2(x - 4) - 9(x - 4) $

Now pull out teh common factor x - 4:

$\large (x - 4)(2x^2 - 9)$

mathstudent55 · Answer

You were close. You have 2x^2 - 4 when it should be 2x^2 - 9 for one of the factors.

anonymous · Answer

oh okay i see what i did wrong! thank you!

mathstudent55 · Answer

You're welcome.

rhondasommer · Answer

^-^ close the question ^_^