vortish
factor the trinomial completely
4u^2+4u15



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hartnn
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tried this ?

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

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

hartnn
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how you could conclude that ? did you find out the value of determinant b^24ac ?

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

hartnn
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4*(15)=60

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

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

vortish
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1086=60 10*6=60 106=4

hartnn
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1086 ??
10 and 6 are correct,
so split +4u into 10u6u
now try...

hartnn
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ohh, 10 & 6

vortish
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(u+10)(u6)

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

vortish
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2u+4u 5

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

vortish
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yes sir

hartnn
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now factor out 2u+5 from that

vortish
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(2u3)=0

hartnn
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2u+5 just disappeared :O :P
(2u+5)(2u3) is your factored form :)

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

vortish
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so the final answer would be (2u+5)(2u3)

hartnn
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its like ab+ac = a(b+c)
(2u+5)*2u + (2u+5)*(3) = (2u+5)(2u3)
and yes.

vortish
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ok thank you sir

hartnn
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welcome ^_^