Help me factor this?

Question

I know its wrong to ask Yahoo Answer to help u do ur homework... but i am completely puzzled so can somebody plzz help me factor this


2x^3+5x^2-8x-20


many thanks to anyone that decides to help me :-) :-)

thank you soo much :-)

u ppl are such great help thanks a lot

Answer 1

You factor by grouping:

[2x^3+5x^2]-[8x+20] ---------------The key here is when you group the last two be careful of the - sign. It changes the signs inside the [ ]
Now what does 2x^3+5x^2 have in common with each other?
x^2? So factor that out.
x^2(2x +5)

Do the second set now.
8x + 20-------------what do they have in common? The numbers are both divisible by 4. Factor out the 4.
4(2x+5)-------------Now put it back together

x^2(2x +5) - 4(2x+5)----------can you see something else in common? Both pieces have a 2x+5 in common. So factor that out.
(2x+5)(x^2-4)-----------If that last step was hard to see then look at it this way.
Let z=2x+5
x^2(t) -4(t)-----------can you see they both have the t in common?
Moving on.
(2x+5)(x^2-4)-----------the first ( ) does not have anything else to factor, but x^2-4 is the difference of perfect squares which means it can be factored again.
(2x+5)(x-2)(x+2)

Hope the explanation helped

Answer 2

I don't think it is wrong! I am happy to help.

Try a grouping (since there are four terms):

(2x^3 + 5x^2) - (8x+20), note sign change
x^2(2x+5) - 4(2x+5), factor out common factors. We see a common factor

(2x+5)(x^2 - 4), and we continue, with difference of squares
(2x+5)(x+4)(x-4).

Done.

Answer 3

f(2) = 16 + 20 - 16 - 20 = 0
Thus (x - 2) is a factor.
Use synthetic division to find other factors
""|2""5""-8""-20
2|""""4""18""20
""|2""9""10""0

(x - 2) (2 x ² + 9 x + 10)
(x - 2) (2 x + 5) (x + 2)

Answer 4

Well, yes, as above, but the last line should be
(2x+5)(x+2)(x-2).
.