## Precalculus (6th Edition) Blitzer

The linear function in slope intercept form that models the total spending, $p\left( x \right)$, by Americans x years after $1950$ is $p\left( x \right)=-0.25x+22$.
From the provided information, the rate of change of decrease in the budget is provided as $0.25\%$. This represents the slope with a negative sign. $m=-0.25$. And the value of c is provided as $22\%$ because the Americans spent $22\%$ of their budget in $1950$ (which is the starting year that shows y the intercept). Substitute the values $m=-0.25$ and $c=22$. The obtained linear model is: $p\left( x \right)=-0.25x+22$. Hence, the linear function in slope-intercept form that models the total spending is $p\left( x \right)=-0.25x+22$.