Confused on a Parallel and Perpendicular Line question?

It says: for what value of k are the two lines 2x+ky=3 and x+y+1 a) parallel? b) perpendicular?

Update:

the second equation is actually x+y=1

1 Answer

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  • TomV
    Lv 7
    8 years ago
    Best Answer

    If two lines are parallel, their slopes are equal. If two lines are parallel, the product of their slopes is equal to -1.

    Line1: 2x+ky = 3 : in slope-intercept form: y = -(2/k)x + 3/k : slope = -2/k

    Line2: x+y = 1 : in slope-intercept form: y = -x + 1 : slope = -1

    Line 1 is parallel to Line 2 if their slopes are equal: -2/k = -1 ==> k = 2

    Line 1 is perpendicular to line 2 if (-2/k)*(-1) = -1 ==> k = -2

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