Download Algebraically Finding the y-intercept with the Slope and another Point

Algebraically Finding the yintercept with the Slope and
another Point
Algebraically Finding the y-intercept
Colleen wants to know how much a chick weighs when it is
hatched. Colleen tracked one of her chickens and found
it grew steadily by about 5.2 grams each day since it was
born. Nine days after it hatched, the chick weighed 98.4
grams. Algebraically determine how much the chick
weighed the day it was hatched.
When the chick was hatched, it was day 0. Thus, we need to find the y-intercept.
y  mx  b
The growth (slope) is 5.2
grams per day
y  5.2 x  b
98.4  5.2  9  b
98.4  46.8  b The equation now has one
Since the growth is constant,
the situation in linear:
The chick weighed 98.4
grams (y) after 9 days (x)
51.6 grams
46.8 46.8
51.6  b
distinct variable. Solve it.
Algebraically Finding a x-Value
Now Colleen wants to know when the chicken will weigh
140 grams. Algebraically find the answer.
Use the slope and y-intercept to write an equation.
Use the SlopeIntercept form:
y  5.2 x  51.6
The 140 grams represents a y value.
140  5.2x  51.6
The equation now
has one distinct
variable. Solve it.
51.6
88.4  5.2x
5.2
5.2
17  x
51.6
Substitute 140 for y
17 Days