a polynomial has one root that equals 2 + i. What is one other root of this polynomial?

Question

ybarrap · Answer

complex roots come in pairs - one the conjugate of the other

anonymous · Answer

It is 2-i  which is the conjugate of 2+i. Complex roots comes in pairs (conjugate of each other). If one of them is a+bi then the other is a-bi

ybarrap · Answer

does this make sense?

anonymous · Answer

oh right! kinda like the inverse

ybarrap · Answer

Yes! But rather than testing vertically to check for more that one y-value for each x in the case of  functions, you test horizontally to see if there is more than one x-value for the same y-value in the case of inverses. These are the vertical test and the horizontal test for functions and inverses, respectively. You got it!