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## vortish 2 years ago factor the trinomial completely 4u^2+4u-15

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1. hartnn

tried this ?

2. vortish

i do not think this can be factored i think it is a prime

3. vortish

i does not make sense 4 can not be factored in t o15

4. hartnn

how you could conclude that ? did you find out the value of determinant b^2-4ac ?

5. hartnn

actually you need to find 2 numbers with product 4*(-15)=60 and sum 4

6. hartnn

4*(-15)=-60

7. vortish

so what your saying i have to find a number that -60 will = 4

8. hartnn

2 numbers whose product is -60 and whose sum is 4 (here, one number is negative)

9. vortish

-1086=-60 10*-6=-60 10-6=4

10. hartnn

-1086 ?? 10 and -6 are correct, so split +4u into 10u-6u now try...

11. hartnn

ohh, 10 & 6

12. vortish

(u+10)(u-6)

13. hartnn

huh ? no... 4u^2 +10u -6u -15 =0 factor out 2u from 1st 2 terms and -3 from last 2 terms, what u get ?

14. vortish

2u+4u -5

15. hartnn

?? (4u^2 +10u) + (-6u -15) =0 2u (2u+5) -3 (2u+5) =0 got this ?

16. vortish

yes sir

17. hartnn

now factor out 2u+5 from that

18. vortish

(2u-3)=0

19. hartnn

2u+5 just disappeared :O :P (2u+5)(2u-3) is your factored form :)

20. vortish

so you can only factor out one of the (2u+5) out of the expression

21. vortish

so the final answer would be (2u+5)(2u-3)

22. hartnn

its like ab+ac = a(b+c) (2u+5)*2u + (2u+5)*(-3) = (2u+5)(2u-3) and yes.

23. vortish

ok thank you sir

24. hartnn

welcome ^_^

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