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by mariah » Sun Jan 15, 2012 5:05 am
Line m and n are perpendicular to each other. Is the abscissa of their intersection -1?
1) The slope of m=1/7
2) n passes through point (0,4)

oa E
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by Anurag@Gurome » Sun Jan 15, 2012 5:15 am
mariah wrote:Line m and n are perpendicular to each other. Is the abscissa of their intersection -1?
1) The slope of m=1/7
2) n passes through point (0,4)

oa E
Abscissa means the x-coordinate.

(1) Slope of m = 1/7 and lines m and n are perpendicular means that the product of their slopes should be -1.
So, slope of n = -7 but the x-coordinate of the intersection may or may not be -1; NOT sufficient.

(2) n passes through point (0,4) but we cannot find the point of intersection of the 2 lines using this info; NOT sufficient.

Combining (1) and (2), equation of line n is (y - 4) = -7(x - 0) but we don't know the equation of line m; NOT sufficient.

The correct answer is E.
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by ArunangsuSahu » Sun Jan 15, 2012 6:48 am
Gradient of the line n=-7=(4-a)/(0-b)

But (a,b) the point of intersection not known

so (E)
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by ronnie1985 » Sun Jan 15, 2012 8:33 pm
S1:-
The slope of m is 1/7 means:-
m: y = (1/7)x+c1 and n: -7x+c2. Since no other info is available it cannot be solved for x or y
Not Sufficient

S2:-
n: y = nx+4, nothing else can be figured out.

Comb:-
m: y = (1/7)x+c1
n: y = -7x+4
Since C1 not known, it cannot be said that the x value of intersection is -1.

(E) is answer.
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