# Math Help!

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1.) Solve the system by graphing. You may use paper or a calculator.

2x - y = 8

x + 3y = 11

2.) The revenue for a certain brand of toothpaste is y = 2.5x where 'x' is the number of tubes of toothpaste sold and 'y' is the total income for selling 'x' tubes. The cost equation is y = 0.9x + 3000, where 'x' is the number of tubes manufactured and 'y' is the cost of producing 'x' tubes. Find the value of 'x' where the company breaks even.

x=?

• Math Help! - ,

1.)

Plot a Cartesian coordinate system

1 equation :

For x = 0

- y = 8 Multiply both sides by - 1

y = - 8

For y = 0

2 x = 8 Divide both sides by 2

x = 4

Mark points ( 0 , - 8 )

x = 0 , y = -8

and ( 4 , 0 )

x = 4 , y = 0

and draw line

2 equation:

For x = 0

3 y = 11 Divide both sides by 3

y = 11 / 3 = 3.67

For y = 0

x = 11

Mark points ( 0, 3.67 )

x = 0 , y = 3.67

and ( 11 , 0 )

x = 11 , y = 0

and draw line

Intersection of this two lines is solution of system.

x = 5 , y = 2

OR

2 x - y = 8

y = 2 x - 8

x + 3y = 11

y = ( 11 - x ) / 3

functions graphs online

When you see list of resulrt click on :

Draw Function Graphs - Plotter - Rechneronline

When page be open in blue rectangle type:

2 x -8

in gray rectangle type:

( 11 - x ) / 3

In options :

Range x-axis from set :

- 3 to 7

Range y-axis from set:

- 15 to 5

and click option draw

2.)

2.5 x = 0.9 x + 3000 Subtract 0.9 to both sides

2.5 x - 0 . 9 = 0.9 x + 3000 - 0.9

1.6 x = 3000 Divide both sides by 1.6

x = 3000 / 1.6 = 1875

• Math Help! - ,

0.9(7x+5)=1.6-(x-3)