How do you solve the system of equations #-1.5x+2.5y=.5# and #2x+y=1.5#?

1 Answer
Jun 9, 2017

See a solution process below:

Explanation:

Step 1) Solve the second equation for #y#:

#2x + y = 1.5#

#-color(red)(2x) + 2x + y = -color(red)(2x) + 1.5#

#0 + y = -2x + 1.5#

#y = -2x + 1.5#

Step 2) Substitute #(-2x + 1.5)# for #y# in the first equation and solve for #x#:

#-1.5x + 2.5y = 0.5# becomes:

#-1.5x + 2.5(-2x + 1.5) = 0.5#

#-1.5x + (2.5 xx -2x) + (2.5 xx 1.5) = 0.5#

#-1.5x - 5x + 3.75 = 0.5#

#(-1.5 - 5)x + 3.75 = 0.5#

#-6.5x + 3.75 = 0.5#

#-6.5x + 3.75 - color(red)(3.75) = 0.5 - color(red)(3.75)#

#-6.5x + 0 = -3.25#

#-6.5x = -3.25#

#(-6.5x)/color(red)(-6.5) = (-3.25)/color(red)(-6.5)#

#(color(red)(cancel(color(black)(-6.5)))x)/cancel(color(red)(-6.5)) = 0.5#

#x = 0.5#

Step 3) Substitute #0.5# for #x# in the solution to the second equation at the end of Step 1 and calculate #y#:

#y = -2x + 1.5# becomes:

#y = (-2 xx 0.5) + 1.5#

#y = -1 + 1.5#

#y = 0.5#

The solution is: #x = 0.5# and #y = 0.5# or #(0.5, 0.5)#