Question

Find the equation of the line through (8,−6) which is perpendicular to the line y=x3−7.

Answer 1

Answer:

y = (-1/3)(x + 10)

Step-by-step explanation:

The slope of the new (perpendicular) line is the negative reciprocal of the slope of the given line, which appears to be 3.  Thus, the perpendicular line has the slope -1/3.

Using the slope-intercept form y = mx + b, and substituting the givens, we obtain:

y = mx + b    =>    -6 = (-1/3)(8) + b, or

-6 = -8/3 + b.  We must solve for the y-intercept, b:

Multiplying all three terms by 3 removes the fraction:

-18 = -8 + 3b.  Thus, -10 = 3b, and so b must be -10/3.

The desired equation is    

y = (-1/3)x - 10/3, or

y = (-1/3)(x + 10)