What is the product of (3a + 2)(4a? - 2a + 9)?
1 answer:
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The correct answer is A.
You have direct variation if x and y are modeled by the equation
In this case, m is the constant of proportionality. So, if the constant has to be 2, the equation becomes
A side note: Actually, option C has a constant of proportionality of two as well, except the roles of x and y are interchanged. I chose option A because usually you want the y = mx form, but the names of the variables are obviously meaningless.
We know that:
is an equation of a circle.
When we substitute x and y (from the pairs we have), we'll get a system of equations:
and all we have to do is solve it for a, b and r.
There will be:
From equations (II) and (III) we have:
and from (I) and (II):
Now we can easly calculate a and b:
Finally we calculate
:
And the equation of the circle is:
is an equation of a circle.
When we substitute x and y (from the pairs we have), we'll get a system of equations:
and all we have to do is solve it for a, b and r.
There will be:
From equations (II) and (III) we have:
and from (I) and (II):
Now we can easly calculate a and b:
Finally we calculate
And the equation of the circle is: