factor 2x^2+12x+30=0 please?

👨🏻‍🏫 學術台 數學
2007-11-09 3:37 pm
I started with
Y=x^2+7x+3
y=-x^2+5x+27
solve using subsitution method

so this is what mymathlab told me to do
x^2+7x+3= -x^2+5x+27

so i got this
2x^2+12x+30=0

but now they want me to factor that and i cant get the right combo of numbers.
it said simplify by dividing both sides by a constant then factor

some one please help me
更新1:

Thank you everyone u made me realize i made a careless mistake. i have a math test in an hour so i hope i dont do that later thank you all

回答 (9)

2007-11-09 3:42 pm
✔ 最佳答案
your final equation should read

2x^2+2x-24=0

which factors to

(2x-6)(x+4)=0
so either
2x-6=0
or
x+4=0

so x=3 or -4
👍 0 👎 0
2007-11-09 3:44 pm
after x^2+7x+3= -x^2+5x+27
you should get
2x^2+2x-24
divide the whole equation by 2
x^2+x-12=0
(x-4)(x+3)
👍 1 👎 0
2016-11-11 11:29 am
that's no longer plenty factoring because it incredibly is plug and examine. only the excellent answer holds actual equations for the x reported. when you come across the excellent answer, you do have got here upon the factoring besides (as i'm going to coach interior the 1st answer): a million:3x2 + 7x = -2 -2, -a million/3 --> 3x2 + 7x + 2 = (x+2)*(x+a million/3)*3 2: x2 - 40 9 = 0 -7, 7 3: x2 + 5x + 4 = 0 -a million, -4 4: 6x2 - 2 = x -a million/2, 2/3 5: x2 - x = 40 two 7, -6 6: x2 - 21x - seventy two = 0 24, -3 7: 7x2 - 7x - 2x + 2 = 0 2/7, a million 8: 3x2 - 2x - 5 = 0.5/3, a million 9: 2a2 - 9a = 5 -a million/2, 5 10: 33x2 - x - 14 = 0 2/3, -7/11 11: 21x2 + 22x - 24 = 0 2/3, -12/7 12: 2x2 + 2x = 60 5, -6 13: x2 + 16x + 40 8 = 0 -4, -12 14: x3 - x2 - 12x = 0 -3, 4, 0 15: 4x2 + 8x + 4 = 0 a million, 2
👍 0 👎 0
2007-11-09 3:57 pm
2x^2+2x-24=0

(2x-6)(x+4)=0
2x-6=0
or
x+4=0
so x=3 or -4
👍 0 👎 0
2007-11-09 3:56 pm
what u do is factor the GCF:2(X^2+X-12)=0,then u factor the equation out but forget the 2 and it should come out as (x+4) and (x-3) which both need to be set to zero to get -4 and 3.
👍 0 👎 0
2007-11-09 3:53 pm
Y=x^2+7x+3 ....(1)
y=-x^2+5x+27 ....(2)

(1) - (2)
0 = x^2+7x+3 - (-x^2+5x+27 )
0 = x^2+7x+3 +x^2 -5x -27
0 = 2x^2 + 2x -24
divide by 2
0 = x^2 + x - 12
0 = (x - 3) (x + 4)

x= 3 or -4
if x = 3, y = 9+21+3 = 33
if x = -4, y = 16-28+3 = -9
👍 0 👎 0
2007-11-09 3:48 pm
The problem 2x^2+12x+30=0 as such, does not have a solution.
ax^2+bx+c=0
a=2 b=12 c=30
b^2-4ac=12^2-4(2)(30)
=144-240 <0 negative
There are no real solutions.
x=[-b + or - (b^2-4ac)]/2a
👍 0 👎 0
2007-11-09 3:46 pm
You did right to get to
x^2+7x+3= -x^2+5x+27, but you messed up the adding and subtraction a little. you will add x^2 to each side, that part is okay, but you are going to subtract 5x and subtract 27 from each side giving you
2x^2+2x-24=0, then you will divide by 2 as it suggests giving you
x^2+x-12=0, which will seperate out nicely to (x+4)*(x-3)=0. leaving x to be -4 or 3.
👍 0 👎 0
2007-11-09 3:44 pm
2x^2+2x-24
x=-4
👍 0 👎 2


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