Writing a rule for this function

Question

x l y

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1 l 20

2 l 16

3 l 12

4 l 8

Answer 1

If you graphed it, it would be a straight line with a negative slope. For every 1 increase in x, y decreases by 4.

The equation is in the form y = mx + b, where m is the slope and b is the y-intercept.

Slope (m) = chg in y/ chg in x, or Δy/Δx. Using any two of the pairs, you could do (20 - 12)/(1 - 3) = 8/-2 = -4 (which we already figured out).

To get b, plug in an (x,y) pair. Ex: 16 =-4(2) + b → b = 16 + 8 = 24.

Equation is y = -4x + 24