9) Because the total number of pencils is 180 and you will use them up in 30 days, the equation will have to equal 0 total pencils when 30 is substituted in for the time factor, or x. This already takes our choice 3 because it doesn’t meet this criteria.
The answer to how many pencils in 20 days could be answered by plugging in 20 for x. Choice 4 cannot work because it results in a negative number of pencils. Choices 1 and 2 use the same equation, so by plugging in 20 it is clear choice 2 is the correct answer.
10) A line parallel to the go en equation would have the same slope, -3, which means choices 1 and 4 are out. Plug in (-2,5) into both choices 2 and 3. Plugging -2 into x in choice 2 gives -5, and in choice 3 gives 5 for the y value. Therefore choice 3 is correct.
(-4-63)\(2x-4-10)-8-10
-67\-18=-3.7
9514 1404 393
Explanation:
1. The general form of a quadratic in standard form* is ...

An example is ...

The constant c is the y-intercept, so is the easiest bit of information to obtain in this form.
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2. The general form of a quadratic in vertex form can be written as ...

An example is ...

The ordered pair (h, k) is the vertex of the parabola, so is easy to obtain in this form. Arguably, it may be easier to identify the line of symmetry, x=h, since that requires looking at only one constant, instead of two.
_____
* In the UK, "standard form" is vertex form.
Answer:
The system of equations is
Step-by-step explanation:
Let
x ----> the number of minutes of calling time
y ----> the monthly cost of the calling plan
we know that
The linear equation in slope intercept form is equal to

where
m is the slope
b is the y-intercept
In this problem
Plan A

substitute
----> equation A
Plan B

substitute
----> equation B
therefore
The system of equations is
So where's the rest of the question?