Marcelo jogs at a speed of 7 miles per hour when there are no hills. He plans to jog up a mountain road which will cause his speed to decrease by r miles per hour. Which of the following expressions represents the time, t, in hours it will take him to jog 13 miles up the mountain road? a. t=13/7r
b. t=7+r/13
c. t=13-r/7
d. t=13/7+r

2.3 hours rounded I suppose.

Step-by-step explanation:

You have jogged 5 miles from the park at a rate of r miles per hour. On your way back to the park your average speed increases by 1 mile per hour.

a. Write an expression for the time t (in hours) it takes to jog 5 miles

from the park as a function of your average speed r (in miles per hour)

b. When you run back to the park, your average speed increases by 1 mph.

Write an expression representing your new speed.

c. Write an expression for the time t(in hours) it takes to jog 5 miles

back to the park.

d. Use your answers to parts a and c to write an expression that gives the total jogging time T (in hours) as a function of your average speed r (in miles per hour) when you are jogging away from the park. Write your answer as a single rational expression.

e. Find the total jogging time if you jogged away from the park at an average speed (r) of 4 miles per hour. Round your answer to the nearest tenth.

hours or 135 minutes

2.3 hours rounded I suppose.

x = ±sqrt(10)

step-by-step explanation:

5 - 2x² = -15

subtract 5 from each side

5-5 - 2x² = -15-5

-2x^2   = -20

divide by -2 on each side

-2x^2   /-2= -20/-2

x^2 =10

take the square root on each side

sqrt(x^2 )=±sqrt(10)

x = ±sqrt(10)

check:

5 - 2x² = -15

+sqrt(10)

5 - 2(sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15

-sqrt(10)

5 - 2(-sqrt(10))² = -15

5 -2(10) = -15

5 -20 = -15

-15 = -15