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would like to solve this system of equation

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substitution method
asked May 4, 2014 in ALGEBRA 1 by anonymous

1 Answer

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Substitution method :

  1. Solve one of the equations for either "x =" or "y =".For example solves the equation for " y " variable.
  2. Replace the " y " value in the first equation by what "y" now equals.  Grab the "y" value and plug it into the other equation.
  3. Solve the new equation for " x ".
  4. Place this new " x " value into either of the ORIGINAL equations in order to solve for "y".  Pick the easier one to work with.
  5. Check:  substitute x = some value and y = some value into BOTH ORIGINAL equations.  If these answers are correct, BOTH equations will be TRUE.

For example :

The system of equations are 4x - 3y = 30 and 2x + y = 30.

solve 2x + y = 30 for y ,Since the coefficient of y is 1.

y = 30 - 2x.

Substitute y = 30 - 2x in 4x - 3y = 30 , and solve for x.

4x - 3(30 - 2x) = 30

4x - 90 + 6x = 30

10x - 90 = 30

10x = 30 + 90

10x = 120

x = 120/10 = 12.

Substitute the value x = 12 in y = 30 - 2x, and solve for y.

y = 30 - 2(12)

y = 30 - 24

y = 6.

Therefore, solution of the system (x, y) = (12, 6).

answered May 12, 2014 by lilly Expert

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