By looking at linear equations we can tell how they will interact in the coordinate plane. which of the following are possible if two linear equations are graphed?
they could be parallel to each other.
they could intersect at two points.
they could be perpendicular to each other.
they could be skew lines.
they could be the same line.

The slope of the line that is perpendicular to the line whose equation is 2x + y = 4 is 1/2; solution: the equation 2x + y = 4; it can be written as y =4-2x; y = -2x+4; this equation is in the form of y = mx + c; where m is the slope of [ the line. thus m = -2; the slope of the line perpendicular to the above line is m*m1 = -1; -2*m1 = -1; m1 = 1/2; ] 
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Ab=dc ac=de ad=bce i hope this !