The mean of 4 numbers is 32. If three of the numbers are 15, 21, and 75, what is the value of the fourth number?
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Answer:
Step-by-step explanation:
First, let's change those variables to x and y, just for the sake of convenience. In order to find the inverse of a function algebraically, switch the x and y coordinates, then solve for the new y. Letting y = A(n) and x = n (we will switch them back when we're done):
y = 3x - 20. This is linear; a line with a slope of 3 and a y-intercept of -20. When we switch the x and the y, we get:
x = 3y - 20. Now we solve for the new y. Begin by adding 20 to both sides:
x + 20 = 3y. Now divide both sides by 3:
, or to write it in slope-intercept form, like the function you started with:
This is also a line, with a slope of 1/3 and a y-intercept of +20/3
Now, replacing:
That is how to write the inverse using function notation. The little -1 as an exponent tells us that this is the inverse of the function A(n).