Answer:
18
Step-by-step explanation:
81π=πr^2
r= 9,-9
9+9=18
6 x 20 x 4 = 480 cm
the surface area is 480 cm
Answer: Company A would be a better deal for number of minutes over 200
Step-by-step explanation:
Let x represent the number of minutes that you would use with either company A or company B.
Company A has a monthly charge of $10 plus 5¢ a minute for each minute of long distance calls. It means that the cost of x minutes of long distance call is
10 + 0.05x
Company B has a monthly charge of $8 plus 6¢ a minute for long distance calls. It means that the cost of x minutes of long distance call is 10 + 0.05x
8 + 0.06x
For Company A to be a better deal, it means that
10 + 0.05x < 8 + 0.06x
10 - 8 < 0.06x - 0.05x
2 < 0.01x
0.01x > 2
x > 2/0.01
x > 200
Slope-intercept form: y = mx + b
(m is the slope, b is the y-intercept or the y value when x = 0 --> (0, y) or the point where the line crosses through the y-axis)
For lines to be perpendicular, their slopes have to be the negative reciprocal of each other. (Basically flip the sign +/- and the fraction(switch the numerator and the denominator))
For example:
Slope = 2 or 
Perpendicular line's slope =
(flip the sign from + to -, and flip the fraction)
Slope = 
Perpendicular line's slope =
(flip the sign from - to +, and flip the fraction)
y = 1/3x + 4 The slope is 1/3, so the perpendicular line's slope is
or -3.
Now that you know the slope, substitute/plug it into the equation:
y = mx + b
y = -3x + b To find b, plug in the point (1, 2) into the equation, then isolate/get the variable "b" by itself
2= -3(1) + b Add 3 on both sides to get "b" by itself
2 + 3 = -3 + 3 + b
5 = b
y = -3x + 5
The equarion to this problem is 30 + 100 + 50x = x