The equation of line t is y = -x + 9/2. Line u includes the point (-8, -1) and is perpendicular to line t. What is the equation of line u?

y = x - 9

Step-by-step explanation:

Keep in mind that the lines t and u are perpendicular, which implies that their slopes are negative reciprocals of one another.  The negative reciprocal of the slope -1 of line t is +1.

Thus we need to find the equation of line u, knowing that the slope of this line is +1.  Starting with the slope-intercept form y = mx + b, we find b:

y = mx + b becomes

-8 = (+1)(-1) + b, or -8 =-1 + b.  Then b = -9, and the desired equation is

y = x - 9