Posted by **Barb** on Wednesday, September 22, 2010 at 10:27pm.

6.Given -2i is a root, determine all other roots of x^4-10x^3+42x^2-88x+80.

A. x= +/- 4, 2i

B.x= -2, +/- 4i

C.x= -4, +/- 2

D.x= -4, 2i

E.x= +/- 4, 2

Please help, I do not understand where to begin.

- PreCalc -
**bobpursley**, Wednesday, September 22, 2010 at 10:30pm
If -2i is a root,then+2i is a root.

so then it is either A or D. Since you know there are 4 roots in a fourth degree polynomial, D does not offer two roots, so A has to be the answer.

- PreCalc -
**bobpursley**, Wednesday, September 22, 2010 at 10:35pm
Now that I look at A, I do not see how -4 can be a root.

checking

256+640+672+88*4+80 is not a root. Thatmeans neither A nor D is a root. Which means none of the answers are then right.

## Answer This Question

## Related Questions

- College Algebra--Still Confused - I have a few problems I need help with and ...
- College Algebra - I have a few problems I need help with and also do have ...
- algebra - Given 3+i is a root, determine all other roots of f(x)=x^4-2x^3-x^2-...
- math - I HAVE THESE ANSWERS FOR THE PROBLEMS. COULD YOU DOUBLE CHECK PLEASE, ...
- math - Could you please solve so I can double check my answers for the practice ...
- maths - Given that√2 is the root of cubic polynomial 6x3 + 2x2-10x -4&#...
- Math - Determine for what value(s) of d the quadratic equation 5x^2-10x+d = 0 ...
- maths2 - Use the discriminant to determine the number of real roots the equation...
- mathematics - Use the discriminant to determine the number of real roots the ...
- math - Solve the equation 4x^3 + 32x^2 + 79x + 60 =0 given that the root is ...

More Related Questions