Adding rational expressions

Find the domain

If sin A and cos A are the roots of the equation ax^2 - bx + c = 0, then a, b and c satisfy the equation: (A) b^2 - a^2 = 2ac, (B) a^2 - b^2 = 2ac, (C) a^2 + b^2 = c^2 ,(D) a^2 + b^2 = 2ac

A: 
The algebra is tedious, but manageable. Use the pythagorean trig identity for sine and cosine set equal to the squares of the 2 roots written in quadratic equation form. Expand and simplify.

simplify i^-156

One-half of a number is equal to the number plus ten

0.5*x=x+10
0.5* x - x =10
-0.5x=10
x=-20

find three Consecutive odd Numbers whose sum is 234

Please check your problem statement. The sum of any odd number of odd numbers (in this case three odd numbers) will be odd, so they cannot add to 234 - an even number

Solve: x+y=3, 2y=3x-4

Solving... 

1) x+y=3
2) 2y=3x-4 

1)...
x=3-y 

2)...
2y=3(3-y)-4
2y=9-3y-4
5y=5
y=1 

1)...
x=3-1
x=2