Set 6 Q27

[arocks]

In the xy-plane, is the slope of line k positive?
(1) Line k passes through the points (-1, -7) and (2, 5).
(2) Line k has equation y = 4x – 3.

Please explain. Thanks.

[josephcho77]

1) you can get the equation y = 4x – 3 using the points (-1, -7)and(2, 5)
The slop is positive

2) y = 4x – 3 (the slop is positive)

Answer is "D"

[arocks]

I understand statement B. Could you elaborate stmt. A. How did you get the equation? Does the line pass through origin - how do we know?

Tnx.

[gabriel]

I understand statement B. Could you elaborate stmt. A. How did you get the equation? Does the line pass through origin - how do we know?

Tnx.

the equation of a line is given by y=mx+c, over here m is the slope and c is the y intercept ..

the given line passes thru the points (-1, -7) and (2, 5)

So we have 2 equations ,

for (-1, -7) we have -7= -1*m+c and
for (2, 5) we have 5 = 2m +c

... solve the 2 linear equations simultaneously to get values of m and c .. hope that helps ..

[agps]

actually it's easier than that. the slope is given by the equation (y2-y1)/(x2-x1).

in this case
(-1, -7) and (2, 5)

(5-(-7))/(2-(-1)) = 12/3 = 4
or
((-7)-5)/((-1)-2) = -12/-3 = 4

[arocks]

Thanks guys. Great responses....Its clear now!