help! slope intercept...?

Question

ok so my math sheet has a bunch of graphs, with multiple choice... it says "which of these equations is shown on the graph?" and the multiple choice is like y=-1/4x=1, and y=4x, and y=-4 ,,, so they are all different. and idk how to find the right awnser, i know how to find the y intercept thing, and that whole x1y1 - x2 y2 thingy but idk how to work it all out. thank youu

Answer 1

oh... this is really easy! =)

Remember... the general line equation is y = mx + b...

where m = slope and b is the y-intercept.... where the line cross the y-axis....

y = -1/4 x +1 has a slope m = -1/4.... and a y-intercept of +1.... the line crosses the y-axis at +1.... or at point (0,1)

y = 4x ... has a slope m = 4.... and a y-intercept of 0....the line crosses the origin... or point (0,0)

so.... look at the graph that they have.... where does the line cross the y-axis?...

look at the b-values first.... if two of the lines both have a y-intercept (b-value) of +2.... crossing the y-axis at point (0, 2)...then you have to start looking at the slopes of the lines.... the m-values...

remember.... m = (change in "y") / (change in "x") or rise over run....

to check the slope of the line that is graphed... pick 'any' point on the line.... Now.... count the steps 'up' (y-steps).... and then the steps across (x-steps).... take the y-steps... and divide that by the x-steps.... that will give you the value of "m" (the slope)....

Now.... knowing the slope of the line... look again at your choices and see which equation has the same m-value as the line.

Hope this helps!!!

Answer 2

Could you describe to me what the pictured graph looks like?

If it is a vertical line, then the pictured graph's equation will be X = some number.

If it is a horizontal line, then the pictured graph's equation will be Y = some number.

If it is a single point on a graph, then the equation will be Y = X = some number. For example, the equation Y = -1/4X = 1 will be a single point, at the coordinates (-4, -4). This is because if -1/4X=1, then X= -4(you get this answer by multiplying both sides by -4, which in turn "cancels out" the left side, since -1/4 * -4 = 1, and 1X = X). If Y=X and X= -4, then Y also = -4.

If it is a diagonal line that goes upward into the top righthand corner(Quadrant I), then the equation will have a positive number in front of the X-variable. For example: The equation Y = 2X will have its diagonal line go upward, since the slope = 2 and 2 is a positive number.

If it is a diagonal line that goes downward into the bottom righthand corner(Quadrant IV), then the equation will have a negative number in front of the Y-variable. This follows the same logic(but reversed) as the above example. If the equation is Y = -3X + 5, then that means that the slope is -3, and since -3 is negative, that indicates a downward-pointing line.

I cannot give you the answer without knowing more info, but hopefully these hints helped at least a little?

Answer 3

The equation y = -1/4x = 1 can be changed to
y = -1/4x - 1 = 0

y = -1/4x - 1 is now in the slope intercept form which is
y = mx + b

To find the y intercept, the graph of the line crosses the y axis when x = 0.
Setting x to zero gives y a value of -1

The slope (m) is -1/4
and the y intercept (b) is -1

Answer 4

Pick a couple points from the line on your worksheet, and see which set of equations they satisfy.

For example, if the point on the line you pick is (1,-3) then it does not satisfy "y=-4" and you know that particular equation does not represent the line.

Answer 5

graph each line and find out which one is pictured on your worksheet.