The average speed of an object moving is its rate of change per time interval. It is equal to the total distance traveled divided by the total time it takes to travel that distance. We calculate the average speed of the olympic record as follows:

The units of the average speed should be miles per hour so we need to convert the distances in to miles and time into units of hours.
distance 1= <span>26 mi
distance 2 = 385 yd ( 1 mile / 1760 yd ) = 0.21875 mi
total distance = 26 + 0.21875 = 26.21875 mi

time 1 = 2 h
time 2 = 9 min ( 1 h / 60 min ) = 0.15 h
time 3 = 21 s ( 1 h / 3600 s ) = 0.0058 h
total time = 2 + 0.15 + 0.0058 = 2.1558 h

average speed = total distance / total time = 26.21875 mi / 2.1558 hr = 12.1620 mi / h</span>

5 0

3 years ago

Write the point-slope form of an equation of the line through the points (-7, 7) and (4, 1).

seraphim [82]

Answer:

Choice B. $\displaystyle y - 7 = -\frac{6}{11} \, (x + 7)$ .

Step-by-step explanation:

Start by finding the slope of this line. Let $(x_1,\, y_1)$ and $(x_2,\, y_2)$ represent two distinct points on a line on a Cartesian Plane. (That is, $x_1 \ne x_2$ .) The slope of this line would be:

$\displaystyle \frac{y_2 - y_1}{x_2 - x_1}$ .

For the line in this question:

$x_1 = -7$ ,
$y_1 = 7$ ;

$x_2 = 4,$
$y_2 = 1$ .

Indeed, $x_1 \ne x_2$ . The slope of this line would thus be $\displaystyle \frac{1 - 7}{4 - (-7)}$ , which is equal to $\displaystyle -\frac{6}{11}$ .

On a Cartesian Plane, the point-slope form of a line that has a slope of $m$ and includes the point $(x_0,\, y_0)$ can be written as:

$y - y_0 = m\, (x - x_0)$ .

(Note the minus signs in this form.)

For the line in this question, $m = \displaystyle -\frac{6}{11}$ . There are two equivalent expressions for its point-slope form:

Using the first point, $y - 7 = \displaystyle -\frac{6}{11}\, (x - (-7))$ . This equation is equivalent to $y - 7 = \displaystyle -\frac{6}{11}\, (x + 7)$ .
Using the second point, $y - 1 = \displaystyle -\frac{6}{11}\, (x - 4)$ .