<p>Yup. If two lines are perpendicular their slopes are negative reciprocals.</p>
<p>To start out, they give the function in point-slope form. In that form, y=ax+b, a is the slope and b is the y-intercept.</p>
<p>In algebra, we learn that if a line is perpendicular to another line, its slope is the opposite reciprocal of the other line. For example, if one line’s slope is 1/3, a perpendicular line must have a slope of -3.</p>
<p>Because f(x)'s slope is 5, and the opposite reciprocal of 5 is -(1/5), a perpendicular line must have -(1/5) as its slope. Look in the answers for g(x) = -(1/5)x + b (any number; no matter how far up or down you shift a line, it’ll still be perpendicular) and you’ll find that the only answer that can fit this is B.</p>
<p>Let me know if anything is still confusing!</p>
<p>When constructing a perpendicular function, you’re trying to make it look so that if you rotate the graph 90 degrees you’ll get a graph of the original function. This requires not only that you take the inverse, but also flip the original function over the y-axis (because when you rotate the page, the y values increase left-wise).</p>
<p>This clears everything up! Thanks for the quick Alg. I refresher!</p>
