# graphing and various equation problems

1.) The national cost "C" in billions of dollars for dental services can be modeled by the linear equation:

C = 2.85n+ 30.52

where n is the number of years since 1990 (Health Care Financing Administration, www.hcfa.gov).

a) Find and interpret the C-intercept for the line.

Put n = 0, we will get

C = 30.52

C-intercept is (0, 30.52)

b) Find and interpret the n-intercept for the line.

Put C = 0, we will get

0 = 2.85n + 30.52

2.85n = - 30.52

n = -30.52/2.85 = -10.71(approximately)

n-intercept is (-10.71, 0)

c) Graph the line for n ranging from 0 through 20.

2.) Demand equation. Helen's Health Foods usually sells 400 cans of ProPac Muscle Punch per week when the price is $5 per can. After experimenting with prices for some time, Helen has determined that the weekly demand can be found by using the equation:

d=600-40p

where d is the number of cans and p is the price per can.

a) Will Helen sell more or less Muscle Punch if she raises

her price from $5?

If she raises the price from $5, the demand will be less.

Let us take p = $6, then

d = 600 - 40*6 = 600 - 240 = 360

Thus the sales will decrease.

b) What happens to her sales every time she raises her

price by $1?

At every $1 increase in price the sales will decrease by 40.

c) Graph the equation.

3.) Marginal revenue. A defense attorney charges her client $4000 plus $120 per hour. The formula R=120n+4000 gives her revenue in dollars for n hours of work.

a) What is her revenue for 100 hours of work?

Put n = 100, we will get

R = 120*100 + 4000 = 12000 + 4000 = 16000

b) What is her revenue for 101 hours of work?

Put n = 101, we will get

R = 120*101 + 4000 = 12120 + 4000 = 16120

c) By how much did the one extra hour of work increase the revenue? (The increase in revenue is called the marginal revenue for the 101st hour.)

Increase = 16120 - 16000 = 120

4.) Gas laws. The volume of a gas is inversely proportional to the pressure on the gas. If the volume is 6 cubic centimeters when the pressure on the gas is 8 kilograms per square centimeter, then what is the volume when the pressure is 12 kilograms per square centimeter?

Let the volume be V and pressure be d then V = kd

Given, if the volume is 6 cubic centimeters when the pressure on the gas is 8 kilograms per square centimeter.

6 = 8k

=> k = 6/8 = ¾

Now, we have to find the volume when the pressure is 12 kilograms per square centimeter.

d = 12, k = ¾

V = kd = (3/4)*12 = 9 cubic centimeters.

5.) Graph the linear inequality:

2x<3y+6

6.) Solve each system by substitution. Determine whether the equations are independent, dependent or inconsistent.

a) y=-3x+19

y=2x-1

Substitute value of y = 2x - 1 in y= -3x+19, we will get

2x - 1 = -3x + 19

5x = 20

X = 4

Now substitute value of x in y = 2x - 1

y = 2*4 - 1 = 8 - 1 = 7

Solution: (4, 7)

System is consistent and independent as it has unique solution.

b) y= -4x -7

y=3x

Substitute y = 3x in y = -4x - 7, we will get

3x = -4x - 7

7x = -7

x = -1

y = 3x = -3

The solution is (-1, -3).

System is consistent and independent as it has unique solution.

7) Solve each system by Addition Method

a) 3x+5y = -11-----------(i)

x-2y = 11-------------(ii)

Mutiply equation (ii) by -3

-3x + 6y = -33

And add to equation (i)

3x + 5y = -11

11y = -44

y = -4

Given x - 2y = 11

x + 8 = 11

x = 3

The solution is (3, -4).

b) 2x=2-4

3x+y=-1

EQUATION NOT CLEAR

8) Solve each system by the Addition Method. Determine whether the equations are independent, dependent or inconsistent.

a) x-y=3

-6x+6y=17

6x - 6y = 18

-6x + 6y = 17

No solution.

Inconsistent and independent

9) Solve each system by Addition Method

a)

Multiply both equations by 63, we will get

27x + 35y = 1701---------(iii)

7x + 18y = 441----------(iv)

Multiply now (iii) by 7 and (iv) by -27

189x + 245y = 11907

-189x - 486y = - 11907

After adding we will get y = 0

(3/7)x + 0 = 27

x = 63

Solution (63, 0)

b) 3x-2.5y=7.125 --------------(i)

2.5x-3y=7.3125-----------------(ii)

Multiply equation (i) by -2.5

-7.5x + 6.25 y = - 17.8125

Multiply equation (ii) by 3

7.5x - 9y=7.3125 = 21.9375

add

-2.75y = 4.125

y = -1.5

2.5x + 4.5 = 7.3125

2.5x = 2.8125

x = 1.125

Solution (1.125, -1.5)

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Sanjay

106417

1.) The national cost "C" in billions of dollars for dental services can be modeled by the linear equation:

C = 2.85n+ 30.52

where n is the number of years since 1990 (Health Care Financing Administration, www.hcfa.gov).

a) Find and interpret the C-intercept for the line.

Put n = 0, we will get

C = 30.52

C-intercept is (0, 30.52)

b) Find and interpret the n-intercept for the line.

Put C = 0, we will get

0 = 2.85n + 30.52

2.85n = - 30.52

n = -30.52/2.85 = -10.71(approximately)

n-intercept is (-10.71, 0)

c) Graph the line for n ranging from 0 through 20.

2.) Demand equation. Helen's Health Foods usually sells 400 cans of ProPac Muscle Punch per week when the price is $5 per can. After experimenting with prices for some time, Helen has determined that the weekly demand can be found by using the equation:

d=600-40p

where d is the number of cans and p is the price per can.

a) Will Helen sell more or less Muscle Punch if she raises

her price from $5?

If she raises the price from $5, the demand will be ...

#### Solution Summary

This solution is comprised of a detailed explanation to answer graphing and various equation problems.