Asked by Sakhya
It takes Lin 1 hour to drive 62 miles,2 hours to drive 130 miles,and 3 hours to drive 195 miles. Write an equation for the relationship.Tell what the variables represent
Answers
Answered by
Reiny
think of having 3 points:
(1, 62), (2, 130) and (3, 195)
slope between first two = (130-62)/(2-1) = 68
slope between last two = (195-130)/(3-2) = 65
So the function is not linear.
We could write a quadratic function, is that what you want?
distance = at^2 + bt +c
for (1,62) --> 62 = a + b + c **
for (2,130) --> 130 = 4a + 2b + c ***
for (3,195) --> 195 = 9a + 3b + c ****
subtract ** from *** : 68 = 3a + b
subtract ** from ***: 65 = 5a + b
now subtract these last two:
-3 = 2a
a = -3/2
in 68 = 3a+b
68 = -9/2 + b
b = 145/2
now back in a+b+c = 62
-3/2 + 145/2 + c = 62
c = -9
distance = (-3/2)t^2 + 145t/2- 9 , where t is time in hours, and distance is miles
(1, 62), (2, 130) and (3, 195)
slope between first two = (130-62)/(2-1) = 68
slope between last two = (195-130)/(3-2) = 65
So the function is not linear.
We could write a quadratic function, is that what you want?
distance = at^2 + bt +c
for (1,62) --> 62 = a + b + c **
for (2,130) --> 130 = 4a + 2b + c ***
for (3,195) --> 195 = 9a + 3b + c ****
subtract ** from *** : 68 = 3a + b
subtract ** from ***: 65 = 5a + b
now subtract these last two:
-3 = 2a
a = -3/2
in 68 = 3a+b
68 = -9/2 + b
b = 145/2
now back in a+b+c = 62
-3/2 + 145/2 + c = 62
c = -9
distance = (-3/2)t^2 + 145t/2- 9 , where t is time in hours, and distance is miles
Answered by
oobleck
I suspect a typo, and he covered 65 miles the 1st hour.
f(t) = 65t
f(t) = 65t
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