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Which of the following lines is perpendicular to 4x + 5y = 9
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19 Jul 2019, 04:40
19 Jul 2019, 04:40
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Which of the following lines is perpendicular to 4x + 5y = 9 on the xy-plane?
A. \(y=\frac{5}{4}x + 2\)
B. \(y=-\frac{5}{4}x+9\)
C. \(y=-4x+\frac{9}{5}\)
D. \(y=\frac{4}{5}x-\frac{4}{5}\)
E. \(y=-\frac{4}{5}x\)
A. \(y=\frac{5}{4}x + 2\)
B. \(y=-\frac{5}{4}x+9\)
C. \(y=-4x+\frac{9}{5}\)
D. \(y=\frac{4}{5}x-\frac{4}{5}\)
E. \(y=-\frac{4}{5}x\)
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GMAT 1: 770 Q51 V44
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Re: Which of the following lines is perpendicular to 4x + 5y = 9
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19 Jul 2019, 05:17
19 Jul 2019, 05:17
1
Expert Reply
Carcass wrote:
Which of the following lines is perpendicular to 4x + 5y = 9 on the xy-plane?
If provided clear algebra on the GRE, attempt to solve the problem algebraically first as it is likely the fastest method.
In this case we remember that the slope-intercept form of the equation of a line is y = mx + b, so we must isolate for y in the given equation.
First, subtract 4x from each side to get 5y = -4x + 9.
Then, divide each side of the equation by 5 to find that y = -4/5x + 9/5.
Finally, remember that the question was asking for the perpendicular slope and that the slopes of perpendicular lines are the opposite sign and reciprocal.
Therefore, the perpendicular line's slope must be 5/4, so select Choice A.
gmatclubot
Re: Which of the following lines is perpendicular to 4x + 5y = 9 [#permalink]
19 Jul 2019, 05:17
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