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Determine slope from a table

A table of corresponding xx- and yy-values represents a linear relationship when the ratio of the change in yy to the change in xx, Δy/Δx\Delta y/\Delta x, is constant; this rate of change is the slope and may be positive, negative, or zero. The slope can be determined from any two ordered pairs in the table, including when xx-values are not consecutive, while distinguishing it from y/xy/x or from the un-reversed change in xx; more advanced treatments of nonlinear data or undefined slope are not included.

Detailed Explanation: Determine slope from a table

Slope tells how much yy changes for each change in xx. For a table, use two corresponding ordered pairs and calculate

m=ΔyΔx=y2y1x2x1.m=\frac{\Delta y}{\Delta x} =\frac{y_2-y_1}{x_2-x_1}.

Always subtract in the same order: if you use the second yy minus the first yy, also use the second xx minus the first xx.

Suppose the table shows:

xxyy
1155
3399
661515

Step 1: Choose two points.
Use (1,5)(1,5) and (6,15)(6,15). The xx-values do not need to be next to each other in the table.

Step 2: Find the change in yy.

Δy=155=10\Delta y=15-5=10

Step 3: Find the change in xx.

Δx=61=5\Delta x=6-1=5

Step 4: Divide the change in yy by the change in xx.

m=ΔyΔx=105=2m=\frac{\Delta y}{\Delta x}=\frac{10}{5}=2

The slope is 2\boxed{2}. This means that for every increase of 11 in xx, yy increases by 22.

Do not calculate yx\frac{y}{x}; slope is the ratio of the changes, ΔyΔx\frac{\Delta y}{\Delta x}. Since the table represents a linear relationship, any two points should give the same slope.

Learn by doing: Determine slope from a table

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Algebra - Find Equivalent - X,Y Chart to Function


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