Tuesday, October 22, 2013

Y=6x-11 -3x-2y=7 solve by substitution |

When simplifying  equations that are done simultaneously it is important to make one variable the subject of the formula to simplify solving the equations. 


We already have y the subject of the formula of the one equation:


`y = 6x -11`


Now we can make y the subject of the formula for the next equation: 


`-3x -2y = 7`


`-3x-7 =2y` (apply inverse operations)


`(-3x-7)/2 = y` (apply inverse operations)


Since we have two equations, we can...

When simplifying  equations that are done simultaneously it is important to make one variable the subject of the formula to simplify solving the equations. 


We already have y the subject of the formula of the one equation:


`y = 6x -11`


Now we can make y the subject of the formula for the next equation: 


`-3x -2y = 7`


`-3x-7 =2y` (apply inverse operations)


`(-3x-7)/2 = y` (apply inverse operations)


Since we have two equations, we can now equate the two equations and solve for x: 


`6x - 11 = (-3x-7)/2`


`2(6x -11) = -3x -7` (inverse operations)


`12x - 22 = -3x -7` (multiply out)


Now get the variable x on the one side, and the constants on the other side:


`12x + 3x = -7+22` (apply inverse operations)


`15x = 15`


`x =1`


Since we know what x is, we can substitute it in the first equation as it is the easiest equation: 


`y = 6(1) -11`


`y = -5`


SUMMARY: `x = 1, y =-5`

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