Exercise 14 Page 248

We are given a table that shows the numbers in millions of active accounts for two social media websites over the past five years.

Let's find an equation of a line of best fit to help us predict how many active accounts Website B will have when Website A has 280 million active accounts. First, we enter the data from the table into our calculator. Start by pressing the STAT button and selecting Edit. Enter the x-values in the first list and the y-values in the second.

Next we press STAT again, go to the CALC menu, and press 4, which corresponds to linear regression. Then we scroll down and select Calculate.

After this process, the calculator returns the slope and the y-intercept of the line of best fit, as well as the correlation coefficient.

We can see that the slope of the line is about - 3.4 and its y-intercept is about 1254. Let's use this information to write the equation of the line of best fit in slope-intercept form. y= - 3.4x+ 1254 Finally, let's substitute 280 into our equation for x and find the value of y. This value will represent how many active accounts Website B will have when Website A has 280 million active accounts.

y = - 3.4x + 1254

Substitute

x= 280

y = - 3.4( 280) + 1254

Multiply

Multiply

y = - 952 + 1254

AddTerms

Add terms

y = 302

Website B will have about 302 million active accounts when Website A has 280 million active accounts.