SOLUTION: meslissa walks 3 miles to the house of a friend an returns home on a bike she averages 4 miles per hour faster when cycling than walking and the total time for both trips is two ho

Question 1049953: meslissa walks 3 miles to the house of a friend an returns home on a bike she averages 4 miles per hour faster when cycling than walking and the total time for both trips is two hours find her walking speed
Found 2 solutions by josmiceli, advanced_Learner:
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
Let = her speed walking
= her speed biking
Let = her time walking
= her time biking
-----------------------------
Melissa walking:
(1)
Melissa biking:
(2)
-----------------------
(2)
(2)
and
(1)
By substitution:
(2)
(2)
Multiply both sides by
(2)
(2)
(2)
(2)
(2)
(2) ( speed has to be positive )
Her walking speed is 2 mi/hr
-----------------------------
check:
(1)
and
(2)
(2)
(2)
(2)
(2)
(2)
(2)
OK

Answer by advanced_Learner(501) (Show Source): You can put this solution on YOUR website!
walking data
speed r
time t
distance 3

cycling data
speed r+4
time 2-t because total time is 2.
distance 3

solve the equations

Solved by pluggable solver: SOLVE quadratic equation with variable

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=100 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 2, -3. Here's your graph:

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