Solving a system by graphing

Question

Solve each system by graphing

 

Y= 5/7x + 4

Y=-1/7x -2

 

 

And Solve by substitution

 

4x + 3y = -8

-8x + y = -12

Answer 1

Graphing:

 

1. Graph both lines and find the point where the two lines intersect.  That point (x,y) is your solution.

 

Substitution:

 

1. Solve either the first or second equation for either x or y.  Here, we'll use the second equation and solve for y. 

 

-8x + y = -12

y = 8x - 12

 

2. Substitute the expression into the other equation for the variable you solved.  Because we solved for y in the second equation, we substitute our expression for y into the first equation.

 

4x + 3(8x - 12) = -8

4x + 24x - 36 = -8

28x - 36 = -8

28x = 28

x = 1

 

3. Now, use the solution you found in step 2 and plug in the value to either of the original equations to find the other variable.

 

4x + 3y = -8

4(1) + 3y = -8

4 + 3y = -8

3y = -12

y = -4

 

The solution for part B is (1,-4).