Answer:
Step-by-step explanation:
a) The equation of a straight line, written in the slope-intercept form is expressed as
y = mx + c
Where c = intercept
Slope, m =change in value of y on the vertical axis / change in value of x on the horizontal axis
change in the value of y = y2 - y1
Change in value of x = x2 -x1
y2 = final value of y
y 1 = initial value of y
x2 = final value of x
x1 = initial value of x
From the graph,
y2 = 80
y1 = 120
x2 = 2
x1 = 1
Slope = (80 - 120)/(2 - 1) = - 40/1
= - 40 miles per hour
To determine the intercept, we would substitute x = 2, y = 80 and m= - 40 into y = mx + c. It becomes
80 = - 40 × 2 + c = - 80 + c
c = 80 + 80 = 160
The equation becomes
y = - 40x + 160
Where
x represents number of time.
y represents distance covered in miles
b) when she starts, x = 0
Therefore,
y = - 40 × 0 + 160
y = 160 miles
She was 160 miles from home when she started and her speed is
- 40 miles per hour
