Question

Lila wrote an equation of the cost for printing brochures, where x represents the number of brochures and y represents the total cost. The total cost for 35 brochures is $41.45. The total cost for 65 brochures is $55.55. Step 1: Write the ordered pairs (35, 41.45) and (65, 55.55). Step 2: Find the slope. M = StartFraction 55.55 minus 41.45 Over 65 minus 35 EndFraction = 0.47 Step 3: Find the y-intercept to write the equation in slope intercept form. Y minus 55.55 = 0.47 (x minus 35). Y minus 55.55 = 0.47 x minus 16.45. Y = 0.47 x + 39.1.

Answer 1

C. Lila made an error in Step 3 when she did not use the x- and y-coordinates from the same ordered pair.

Explanation:

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Answer 2

y = 0.47x + 25

y1 = 41.45 and not 55.55

Explanation:

Given that:

x = number of brochures

y = total. Cost

Total cost of 35 brochures = $41.45

Total cost of 65 brochures = $55.55

The ordered pairs :

(x1, y1) ; (x2, y2)

x1 = 35 ; y1 = 41.45 ; x2 = 65 ; y2 = 55.55

(35, 41.45), (65, 55.55)

The slope :

Slope (m) = change in y / change in x

m = (y2 - y1) / (x2 - x1)

m = (55.55 - 41.45) / (65 - 35)

m = 14.1 / 30

m = 0.47

The y intercept :

y - y1 = m(x - x1)

y - 41.45 = 0.47(x - 35)

y - 41.45 = 0.47x - 16.45

y = 0.47x - 16.45 + 41.45

y = 0.47x + 25

Lila incorrectly chose 41. 45 as y1