18. If 1 and –6 are two of the roots of 6x^4 + 31 x^3 − 33x^2 − 16x + 12, then what are the other two?
A. -2 and 2/3
B. ½ and -2/3
C. -1 and 6
D. 2 and 3/2
Use synthetic division
1 | .....6.....31.....–33.....–16.....12
..................6.......37........4...–12
-------------------------------------------------
–6|....6......37........4.....–12.....| 0
..............–36.......–6......12
-----------------------------------------
........6........1.......–2.....| 0
We are left with 6x² + x – 2 = (3x + 2)(2x – 1)
The other roots are –2/3 and 1/2, B
If 1 and -6 are roots, then x-1 and x + 6 must be factors. Divide the original polynomial by each factor to find the remaining quadratic equation.
Divide 6x^4 + 31 x^2 - 33x^2 - 16x + 12 by x - 1 : 6x^3 + 37x^2 + 4x - 12
Divide 6x^3 + 37x^2 + 4x - 12 by x + 6: 6x^2 + x - 2
This factors into (3x + 2)(2x - 1)
So the remaining zeroes are -2/3 and 1/2, answer B
-1 | 6 31 -33 -16 12
-6 -26 59 -43
6 26 -59 43 -31
You must've copied the equation wrong.
if 1 and -6 are roots, then (x - 1)(x + 6) are factors
divide the given polynomial by the product of (x - 1)(x + 6)
(6x^4 + 31 x^3 â 33x^2 â 16x + 12) / (x - 1)(x + 6) = (6x^4 + 31 x^3 â 33x^2 â 16x + 12) /(x^2 +5x - 6)
x^2+5x-6) 6x^4+31x^3â33x^2â16x+12(6x^2
...............6x^4+30x^3-36x^2
______________________________________
........................x^3 + 3x^2 - 16x (x
........................x^3 + 5x^2 - 6x
________________________________
.................................-2x^2 - 10x + 12(-2
.................................-2x^2 - 10x + 12
___________________________________
............................................0
The quotient is 6x^2 + x - 2
=> 6x^2 + 4x - 3x - 2 = 0
=> 2x(3x + 2) - 1(3x + 2) = 0
=> (2x - 1)(3x + 2) = 0
x = 1/2 and - 2/3
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Answers & Comments
Verified answer
Use synthetic division
1 | .....6.....31.....–33.....–16.....12
..................6.......37........4...–12
-------------------------------------------------
–6|....6......37........4.....–12.....| 0
..............–36.......–6......12
-----------------------------------------
........6........1.......–2.....| 0
We are left with 6x² + x – 2 = (3x + 2)(2x – 1)
The other roots are –2/3 and 1/2, B
If 1 and -6 are roots, then x-1 and x + 6 must be factors. Divide the original polynomial by each factor to find the remaining quadratic equation.
Divide 6x^4 + 31 x^2 - 33x^2 - 16x + 12 by x - 1 : 6x^3 + 37x^2 + 4x - 12
Divide 6x^3 + 37x^2 + 4x - 12 by x + 6: 6x^2 + x - 2
This factors into (3x + 2)(2x - 1)
So the remaining zeroes are -2/3 and 1/2, answer B
-1 | 6 31 -33 -16 12
-6 -26 59 -43
6 26 -59 43 -31
You must've copied the equation wrong.
if 1 and -6 are roots, then (x - 1)(x + 6) are factors
divide the given polynomial by the product of (x - 1)(x + 6)
(6x^4 + 31 x^3 â 33x^2 â 16x + 12) / (x - 1)(x + 6) = (6x^4 + 31 x^3 â 33x^2 â 16x + 12) /(x^2 +5x - 6)
x^2+5x-6) 6x^4+31x^3â33x^2â16x+12(6x^2
...............6x^4+30x^3-36x^2
______________________________________
........................x^3 + 3x^2 - 16x (x
........................x^3 + 5x^2 - 6x
________________________________
.................................-2x^2 - 10x + 12(-2
.................................-2x^2 - 10x + 12
___________________________________
............................................0
The quotient is 6x^2 + x - 2
=> 6x^2 + 4x - 3x - 2 = 0
=> 2x(3x + 2) - 1(3x + 2) = 0
=> (2x - 1)(3x + 2) = 0
x = 1/2 and - 2/3