SOLUTION: If the lines whose equations are 3x+y-8=0 and -2x+by+9=0 are perpendicular, what is the value of b?

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Question 317695: If the lines whose equations are 3x+y-8=0 and -2x+by+9=0 are perpendicular, what is the value of b?
Answer by Alan3354(69443) About Me  (Show Source):
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If the lines whose equations are 3x+y-8=0 and -2x+by+9=0 are perpendicular, what is the value of b?
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Find the slope of 3x+y-8=0
y = -3x + 8
slope = -3
The slope of lines perpendicular is the negative inverse, m = +1/3
Put -2x+by+9=0 into slope-intercept form (that means solve for y)
by = 2x - 9
y = (2/b)x - 9/b
2/b is the slope, and it = 1/3
2/b = 1/3
b = 6