Exercise 21 Page 202

Consider the given equation of a line. y= -2x-8 To find the slope perpendicular to this line, we need to find the negative reciprocal of -2.

m_1 * m_2 = -1

Substitute

m_1= -2

-2 * m_2 = -1

DivEqn

.LHS /(-2).=.RHS /(-2).

m_2 = -1/-2

DivNegNeg

- a/- b=a/b

m_2=1/2

We have found that 12 is the negative reciprocal of -2. Using this information we can write a general equation in point-slope form for the lines perpendicular to the given line. y- y_1 = 1/2(x- x_1) Since we know that point P( 4, 4) should be contained in the perpendicular line, we can substitute it for ( x_1, y_1). By doing so, we will be able to write the equation of the line perpendicular to the given one, and containing point P. y- 4 = 1/2(x- 4)