3x^4 + 5x² - 2 = 0
Let y = x²
3y² + 5y - 2 = 0
3y² + 6y - y - 2 = 0
3y(y+2)-1(y+2) = 0
(y+2)(3y-1) = 0
y = {-2, 1/3}
x = sqrt(y)
x = {±(√2)i, ±1/√3}
Using the quadratic formula:
ax² + bx + c = 0
x = (-b±√(b²-4ac))2a
3(x²)² + 5x² - 2 = 0
a = 3
b = 5
c = -2
x² = (-5±√(5²+24))/6
= (-5±√49)/6
= (-5±7)/6
= {2/6, -12/6}
= {1/3, -2}
x = {±√(1/3), ±√(-2)}
x = {±(√2)i, ±1/√3}
2007-12-03 09:24:45
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answer #1
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answered by gudspeling 7
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Since you have no odd powers of x, try replacing k = x²
3k² + 5k - 2 = 0
Now you can factor this easily as:
(3k - 1)(k + 2) = 0
So k = 1/3 or k = -2
Substitute x² back in and you have:
x² = 1/3 or x² = -2
Taking the square root of each of these you get:
x = ±â(1/3) = ±(â3) / 3
x = ±â(-2) = ±(â2)i
You have 4 roots (2 real and 2 imaginary)
Real roots:
â3 / 3
-â3 / 3
Imaginary roots:
â2 i
-â2 i
2007-12-03 17:22:33
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answer #2
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answered by Puzzling 7
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Use the Quadratic Formula: x equals negative b, plus or minis square root b squared minus 4ab all over 2a. First, subtract 2 from both sides. now u have 3x^4 + 5x^2=2. the first term is a, the second term is b and the third term is c. substitute all a, b and c with the quadratic formula. that should give you the answer. = )
2007-12-03 17:24:11
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answer #3
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answered by Agent 47 2
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Instead of x^2, replace it with t = x^2.
You then look at the equation:
3t^2 + 5t - 2 = 0
Solutions:
t = (-5 + sqrt(5*5 - 4*3*(-2)) / (3*2) = (-5 + 7) / 6 = 2 / 6 = 1 / 3 = 0.333...
t = (-5 - sqrt(5*5 - 4*3*(-2)) / (3*2) = (-5 - 7) / 6 = -12 / 6 = -2
Since t = x^2:
x = sqrt(-2) = 2*i or -2*i
or
x = sqrt(1/3).
Hope this helps. :)
* sqrt = square root *
2007-12-03 17:26:35
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answer #4
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answered by pera detlic 2
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PEMDAS! Please Excuse My Dear Aunt Sally! 0
2-2 = 0 so 4=5x^0 = 0 so 3x^0 = 0. Its been a long time. don't laugh at me if I'm wrong. lol!
2007-12-03 17:23:27
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answer #5
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answered by HealthyHealth 1
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what are you trying to solve for and what are you using. I'm pretty good at this, so just let me know
2007-12-03 17:21:30
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answer #6
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answered by hockeyplyr545 1
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what the heck are you trying to do?
find the roots, solve for x? i have no idea.
2007-12-03 17:20:38
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answer #7
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answered by Anonymous
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answer is 20
2007-12-03 17:21:43
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answer #8
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answered by joegramma 1
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??? >123<323....444 :-)
2007-12-03 17:21:22
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answer #9
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answered by http://www.techhairball.com 2
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thats pretty scary
2007-12-03 17:21:21
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answer #10
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answered by adge_505 1
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