Let x represent the # of 2-hour days and y the # of 3-hour days. Jimmy's study was spread over 10 days. Thus, x + y must sum up to 10. Also, 2x + 3y must sum up to 22 hours.Our system now looks like this:

x + y = 10

2x + 3y = 22

Multiply the first equation by -2: -2x - 2y = -20 Add the 2nd equation to this:

-2x - 2y = -20

2x + 3y = 22

------------------ y = 2 So Jimmy had 2 3-hour study days and 8 2-hour study days.

Note how these figures add up to 22: 6 + 16 = 22

Hope that help!

5 0

3 years ago

Write the equation of the circle that has a diameter with endpoints (6,-1) and (0,-7).

Yanka [14]

$d = \sqrt{(x_2 - x_1)^{2} + (y_2 - y_1)^{2}}$
$d = \sqrt{(0 - (-1))^{2} + (-7 - (-1))^{2}}$
$d = \sqrt{(0 + 1)^{2} + (-7 + 1)^{2}}$
$d = \sqrt{(1)^{2} + (-6)^{2}}$
$d = \sqrt{1 + 36}$
$d = \sqrt{37}$
$d = 6.083$

6 0

4 years ago