algebra

posted by .

x^2+3x-12=0
I need to factor this and thought I knew how, but I can't figure this one out. Factors of 12 are 1,12; 2,6; 3,4 and when I subtract these I don't get the 3 I need for the 3x. Am I overlooking something? My other problems were easy, so I don't think this would be a decimal or a fraction. Thank you for any help!!

• algebra -

lets do it by completion of the square:

x^2+3x+9/4=12+9/4
(x+3/2)^2=57/4

x=-3/2+-sqrt 14.25

so it factors, but into irrational numbers.

(x+1.5+sqrt 14.25)(x+1.5-sqrt 14.25)=0

nice, huh?

Similar Questions

1. math

how would you simplify y= (x^5-32)/(x-2)?
2. Math

What do we call the numbers that cannot be arranged into 2-row arrays?
3. Chemistry

I Have Two Questions 1)How would you calculate the number of nanometers in 8.1 cm?
4. math,help

What does it mean to factor an algebraic expression into prime factors?
5. bobPursley2...the other one

Problem 2: (x+2)/(2x^2+5x+2) - (x-3)/(2x^2-5x-3) What I did: 2x^2+5x+2 factors are (2x+1)(x+2) 2x^2-5x-3 factors are (2x+1)(x-3) Then: (x+2)/(2x+1)(x+2) - (x-3)/(2x+1)x-3) So the common denominator is (2x+1)(x+2)(x-3) using that combine …
6. Math

I have 4 math problems that need to be solved by using factoring. I am unable to figure the following out. I have used the FOIL method but it seems not to be working out. I appreciate any help I can get. Thanks ^ exponet 3x^3-7x^2+2x …
7. help

i need help solvin this quadratic equation 2x^2+x-6=0 1/3x^2+8x-3=0 Try to factor, then set the factors equal to 0 to find possible solutions for x. For the first one: 2x^2 + x - 6 = 0 Factors are: (2x - 3)(x + 2) = 0 Setting the factors …
8. Algebra

ello i need help factoring I haven't had factorin sense Algebra one and now am in Algebra two and our school is screwed up were they shove in a year of Euclidean Geometry and Basic Trig inbetween first two years of Algebra... so i …