(x-5)(3x+4)=0
What steps do I take to solve it?
2007-05-17
12:34:39
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12 answers
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asked by
Jenny
3
in
Science & Mathematics
➔ Mathematics
x-5)(3x+4)=0
What steps do I take to solve it?
EDIT: After I FOILed it, I got 3x^2-11x-20
And after using the quadratic formula I ended up with (11±√361)/6
How do I solve from here?
2007-05-17
12:45:49 ·
update #1
I dont know if I FOIL and use the quadratic equation, or if I simply find out which bracket equals zero.
Anyways, thanks everyone for your help.
2007-05-17
12:53:14 ·
update #2
I believe you have to FOIL it
2007-05-17 12:38:05
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answer #1
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answered by Jen 4
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Use the zero product rule: If ab = 0, then a = 0 or b = 0. Since you have the product of two things equal to 0. Set them both equal to 0 and solve.
(x - 5)(3x + 4) = 0
x - 5 = 0 or 3x + 4 = 0
Add 5 to both sides of the equal sign for the first one to get x = 5.
For the second one, subtract 4 from both sides to get 3x = -4. Finally, divide both sides by 3 to get x = -4/3. So your answers are x = 5 and x = -4/3. Hope this helps.
2007-05-17 19:41:16
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answer #2
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answered by Lee 3
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The long and unnecessarily complicated way is by multiplying out everything to get rid of the parentheses, and then using the quadratic equation.
The fast and easy way is as follows:
- Realize that when you're multiplying two things together, the only way you can end up with 0 is if one of the two things you're multiplying is zero.
- From this, you realize that either (x-5) = 0, or (3x+4) = 0.
x-5 = 0 when x = 5
3x+4 = 0 when x = -4/3
Hence, the two possible answers are x=5 and x=-4/3.
Hopefully that helps!
2007-05-17 19:40:54
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answer #3
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answered by Bramblyspam 7
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FOIL means First Inside Outside Last. In your first brackets multiply the first number or variable in the equation bby the whole second brackets. Then do the same with the second number or variable in the first bracket. Example:
(x+1)(x+2):
First with the x:
x*x=x^2 (x squared)
x*2=2x
Now with the 1:
1*x=x
1*2=2
Since the first bracket had x+1 that means you add both brackets:
(x^2+2x)+(x+2) = x^2+2x+1+2=x^2+3x+2
Plug in your numbers and solve with these steps.
2007-05-17 19:38:08
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answer #4
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answered by Cool Nerd At Your Service 4
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to make this equation happens, x-5 or 3x+4 must equals to 0 ( because any numbers multiply with 0 equals 0, right?)
which means: x-5=0 or 3x+4=0
* with x-5=0, add 5 to both sides. x=5.
* with 3x+4=0, minus 4 from both sides, u'll have: 3x= - 4
Now, devided both sides by 3. x=-4/3.
So the final solutions are: 5 and -4/3
2007-05-17 19:45:31
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answer #5
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answered by Salinda M 2
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Let each factor = 0
x - 5 = 0, x = 5
3x + 4 = 0, 3x = -4, x = -4/3
2007-05-17 19:38:13
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answer #6
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answered by richardwptljc 6
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if (x-5)(3x+4)=0 it means that also x-5=0 and 3x+4=0 Now all you have to do is calculate.
x=5,x= -4/3
2007-05-17 19:42:54
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answer #7
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answered by Andra 2
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do you need to find the values of x?
then one of the brackets must equal 0, but you do not know which one, therefore:
1st: x-5=0 --> x=0+5 --> x=5
2nd: 3x+4=0 --> 3x=-4 --> x= -4/3
2007-05-17 19:40:30
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answer #8
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answered by elf 2
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use foil
(x-5)(3x+4)=0 write origional
foil= first
outside
inside
last
3x squared
4x
-15x
-20
the answer is...
3x squared -11x-20
hope that helpes =p
2007-05-17 19:43:07
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answer #9
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answered by Anonymous
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(x-5)=-5x
(3x+4)=7x
so its the same as -5x times 7x...find out what -5 times 7 is then figure out what x should be
2007-05-17 19:43:57
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answer #10
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answered by Jordan 1
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Expand and use the quadratic formula.
2007-05-17 19:38:58
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answer #11
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answered by Fuss 1
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