Solving Systems by Substitution Steps

What is the first step in solving a system by Substitution?

• Make sure both equations are in standard form.

• Make sure at least one equation is solved for one variable.

• Make sure both equations are in slope-intercept form.

Why does substitution help us solve a system of equations?

• It changes one variable to an expression using the other variable, so we can solve an equation that only has one variable at a time.

• It creates a problem with fewer steps.

• It puts both equations in slope-intercept form for easy graphing.

TRUE or FALSE: When both equations have the same variable isolated (both y = or both x = ), substituting the first into the second ends up looking like you just set the two equal to each other.

• TRUE

• FALSE

Which option shows the CORRECT substitution for this system?

Solve the following system by substitution.  What is the solution?

• (1, -2)

• (-2, 1)

• (-4, 1)

• (2, 1)

• (1, -4)

• (1, 4)

• (-4, -7)

• (-7, -4)

Solve the system by substitution

• (1,1)

• (-1,1)

• (-1,0)

• (1,-1)

Solve this system by substitution.

• (1,-4)

• (1,4)

• (-4,-7)

• (-7,-4)

Solve the system by substitution.
 
5x + 4y= −14
y =  −7x  −  15 

• (-2, -1)

• (1, -2)

• (-2, 1)

• (-1, -2)

Solve this system by substitution.

• (1, -4)

• (1, 4)

• (-4, -7)

• (-7, -4)