Subtract the complex numbers: (-2 + 12i) - (-1 - 9i) A) -1 + 3i
B) -3 + 3i
C) -1 + 21i
D) -3 + 21i

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  C)  -1 +21i

Step-by-step explanation:

For many purposes, "i" can be treated as though it is a variable. Collect terms in the usual way.

  (-2 +12i) -(-1 -9i) . . . . given

  = -2 +12i +1 +9i . . . . use the distributive property to eliminate parentheses

  = (-2+1) +(12i +9i) . . . group like terms

  = -1 +21i

x= -3 and

step-by-step explanation:

to find the roots of a cubic, use division or factoring to find the factors then set equal to 0. as this is a difference of cubes, it factors into

where a is the cube root of .

here   this is 27 and the cube root of 27 is 3. so we write using the form:

.

set each factor to 0 and solve for x.

x-3=0

x=3

the quadratic expression does not factor and must be solved using the quadratic formula.

where a = 1, b=3, and c=9

this cubic has two complex roots.