Question

monthly sales & advertising costs
the scatterplot and trend line show a positive
correlation between advertising costs and sales.
the slope was found using the points (6.4, 117) and
(6.6, 120). what is the value of b in the equation of the
trend line?
$y = 15x + b$

Explanation:

Step1: Substitute the values of \(x\) and \(y\) into the equation

We know the equation \(y = 15x + b\). Let's take the point \((x = 6.4,y = 117)\) (we could also take \((6.6,120)\)). Substitute \(x = 6.4\) and \(y=117\) into the equation:
\(117=15\times6.4 + b\)

Step2: Calculate the value of \(15\times6.4\)

\(15\times6.4=(10 + 5)\times6.4=10\times6.4+5\times6.4=64 + 32=96\)
So the equation becomes \(117 = 96 + b\)

Step3: Solve for \(b\)

Subtract 96 from both sides of the equation \(117-96=b\)

Answer:

\(21\)