All courses Math Foundations · MF.GR.7 46 of 60
Match and compare words, tables, graphs, and simple equations that represent the same relationship.

Match a table to its rule

Problem
A table maps \(x\)-values \(0,~1,~2,~3\) to \(y\)-values \(2,~6,~10,~14\). Determine the equation represented by the table.
Relationship Table: x and y with 4 rows. Open full size
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Hint

Look at the row where x = 0 to find the starting value, then check how much y increases each time x goes up by 1.

A table and an equation match only if they have the same starting value and the same rate of change.

Solution walkthrough

01

Read the table pairs

\[(x,y)=(0,2),(1,6),(2,10),(3,14)\]

The inspected table supplies consecutive x-values and their outputs.

02

Find the rate of change

\[(6-2)/(1-0)=4;~(10-6)/(2-1)=4;~(14-10)/(3-2)=4\]

Every one-unit increase in x raises y by four, so the coefficient is four.

03

Find the starting value

\[x=0~⇒~y=2~⇒~b=2\]

The zero-input row gives the constant term in y=mx+b.

04

Build and check the equation

\[y=4x+2;~x=3~⇒~4(3)+2=14\]

Combining rate four and start two reproduces the final row.

05

Report the equation

\[y~=~4x~+~2\]

The equation represents both the constant rate and starting value in the table.

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Another way

  1. Assume y=mx+b, use (0,2) for b, then use (1,6) to solve 6=m+2.

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Common mistake

Do not write y=4x and omit the starting value; the table gives y=2 when x=0.

Solution walkthrough video