The letter C stands for the Circumference of the circle
The result after combining like terms is: 
Step-by-step explanation:
Given expression is:

The like terms are those terms with whom the variable or product of variables is same.
As in the given expression, first and third, both terms have x^2y so both terms are like terms
Combining like terms, means the indicated operation is performed on them
So,
Combining like terms:

Hence,
The result after combining like terms is: 
Keywords: Expressions, polynomials
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A.) 0.55
This is because the probability has to com out to 1 (technically 100%) so, 1-0.45 is 0.55 (these could all be percentages if you multiply them by 100)
If you're completing the square the answer is in the image.
expression
x^2 + 5x - 5=ax^2+bx+c
a=1, b=5, c=-5, and you can solve it that way.