Emergency Help i dont understand factoring!?

Ive been having a lot of trouble in alg 2 lately and ive come to the conclusion i just dont understand FACTORING.


Please help im so desperate. Im getting a tutor soon( but i am an honor roll student who made a C in algebra.)





So i understand how to factor the simple stuff like this.


x^2+6x+8


it would be


(x+4)(x+2)





but i dont understand this


2x^2-x-10


=[


please help me i rly rly need it and its already 10:45 here ive been trying this for hours.


thanks

Emergency Help i dont understand factoring!?
Okay. what you need to do is factor by grouping.





You take the 2 from the 2x^2 and multiply by -10. it equals 20.


Then you take the 20 and find the two factors that equal -1 from the -x. they are -5 and 4.





so now your equation is: 2x^2-5x+4x-10


you take out the factors of each group.


so you have x(2x-5)+2(2x-5)


and you put the numbers on the outside together and the parentheses should always be the same and that is your other.





(x+2)(2x-5)





get it yet? If you need more help, ask.
Reply:Another method is:


Try different combinations of binomials as the factors, using factors of the coefficient of the first polynomial term (this coefficient is the 2 in 2x^2 in this case) as the coefficients of the first terms in the binomials, and factors of the number term (the 10) as the last terms in the binomials, based on FOIL (First, Outside, Inside, Last), using pairs of factors that multiply to the number for the x^2-term and the number-term of the polynomial.


-- For the signs in the binomials, if the given polynomial has a minus sign for its last term, the binomials would have one plus sign and one minus sign. If given polynomial has minus and then plus, both binomials would have minus.


-- Use FOIL to multiply out the binomials that you have created, to see if you get the middle term that is in the given polynomial. If not, try another possible pair of binomial factors.





So for the given polynomial 2x^2-x-10:


-- The coefficients of the first terms of the binomial factors would be factors of 2, which are 1 and 2.


-- The last terms of the binomials would be factors of 10 and could be 1 and 10, or 2 and 5.


-- Since the second sign is minus, one binomial factor would have plus and the other would have minus.





The possibilities of answers include (2x+2)(x-5); (2x+5)(x-2); (2x-2)(x+5); (2x-5)(x+2); and similar pairs of binomials using 1 and 10 as the factors of 10. See which one results in a middle term of -x when multiplied out by FOIL, and that would be the correct answer.
Reply:2*x^2 - 1x - 10


general form of factors


(x + a)(2x + b)


2x^2 + (2ax + bx) + ab





equate like terms


2a+b = -1


ab = -10


solve the two above equations


a=2


b=-5


therefore the factors are


(x+2)(2x-5)





check your math


2x^2 +4x -5x -10


2x^2 -x -10


2x^2 -x -1
Reply:The tough part is that one of your x's will need to be a 2x. :)





Here is the problem factored. As an honor student, see if you understand why it works :)





(x+2)(2x - 5)





Good Luck!
Reply:use the quadratic formula, (-b+/-(b^2-4ac)^1/2)/2a