Posted by Nick on Thursday, December 13, 2007 at 7:41pm.
Solve x^4  12x  5 = 0 given that 1 + 2i is a root.
I’ve used synthetic division to get the answers x = 1 +/ 2i , 1 +/ sqrt 2
I’ve having trouble checking the answers though because of that imaginary number. How can I check these kind of problems?

Algebra II  Damon, Thursday, December 13, 2007 at 8:16pm
If (1+2i) is a solution, its complex conjugate (12i) must be a solution.
In other words
x = 1+2i
x = 12i
are solutions
so
x+12iand x+1+2i are both factors
so their product should be a factor
I get x^2+2x+5
now do your division
I get
x^22x1
well
that is
(x1)(x1)
so my four solutions are those two complex conjugates and x=1 and x =1 again
Answer This Question
Related Questions
 Algebra  please help me with this question and check my answers. Solve the ...
 algebra  The equation f(x) = 3x^3 + 10x^2  16x  32 has a root at x = 4 a) ...
 Pre Calc (For Reiny)  Thanks so much your method worked perfectly! My solution ...
 Algebra  Divide using long division or synthetic division. (21x^3  7)/(3x  1...
 Algebra  Divide using long division or synthetic division. (21x^3  7)/(3x  1...
 Pre Calc  I am familiar with this type of problem but can't seem to get the ...
 trig  The equation f(x) = 3x^3 + 10x^2  16x  32 has a root at x = 4 a) Find ...
 9th grade algebra (completing square)  Can you check the following? A1. (2x + 3...
 Algebra HELP  h(x)= 3x^(5) + 2x^(4) + 15x^(3) + 10x^(2)  528x  352 for this ...
 math  determine the area of triangle abc when side ab= square root of x, side ...
More Related Questions