The circumference of a circle -
The radius is
10 in.
The vertex is the high point of the curve, (2, 1). The vertex form of the equation for a parabola is
.. y = a*(x -h)^2 +k . . . . . . . for vertex = (h, k)
Using the vertex coordinates we read from the graph, the equation is
.. y = a*(x -2)^2 +1
We need to find the value of "a". We can do that by using any (x, y) value that we know (other than the vertex), for example (1, 0).
.. 0 = a*(1 -2)^2 +1
.. 0 = a*1 +1
.. -1 = a
Now we know the equation is
.. y = -(x -2)^2 +1
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If we like, we can expand it to
.. y = -(x^2 -4x +4) +1
.. y = -x^2 +4x -3
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An alternative approach would be to make use of the zeros. You can read the x-intercepts from the graph as x=1 and x=3. Then you can write the equation as
.. y = a*(x -1)*(x -3)
Once again, you need to find the value of "a" using some other point on the graph. The vertex (x, y) = (2, 1) is one such point. Subsituting those values, we get
.. 1 = a*(2 -1)*(2 -3) = a*1*-1 = -a
.. -1 = a
Then the equation of the graph can be written as
.. y = -(x -1)(x -3)
In expanded form, this is
.. y = -(x^2 -4x +3)
.. y = -x^2 +4x -3 . . . . . . same as above
Since we know that 1/4 is equal to 25%, or 0.25 in decimal form, we are able to work with 0.75 in the expression.
We are told to use j as the original price of the jeans, so we can set up the expression:
to represent the cost of the jeans with the discount.
Then to simplify, we simply take out j as a common factor, and solve what's in the parentheses:
or 
Using this equation, we can solve for the b part of the question. If the pair of jeans originally costs $60, plug in 60 to where j is in the expression:
Therefore, the cost of the jeans after the discount is C) $45.
