How do you solve the following linear system: # x + 6y = 28 , 6x - 5y = -1 #?

1 Answer
Apr 12, 2018

See below

Explanation:

We will use elimination to solve this linear system.

Firstly we need to get same numbers but opposite sign from that same number.

In #x + 6y=28# /#* (-6)# (multiply the first equation with #-6#)
#6x-5y=-1#

We get,

#color(blue)(-6x)-36y=-168# ------- #color (red) (equation 1#
#color(blue)(6x)-5y=-1# ------ #color(blue)(equation 2)#

You can see that #-6x# and #6x# are opposites so we cancel them but firstly write the following,

#cancel(-6x)-36y+cancel(6x)-5y=-168-1#

#-41y=-169# From here

#y=-169/-41#

#y=169/41#

It's now

#-6x-36y=-168# ------- #color (red) (equation 1#
#y=169/41# ------ #color(blue)(equation 2)#

Basically just add #y=169/41# into # y# in the first equation

#-6x-36*169/41=-168#

#-6x-6084/41=-168#

#-6x=-168+6084/41#

#-6x=-804/41#

#x=(804/41)/(6/1)#

#x=cancel804/cancel246#

#x=134/41#

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Final result:

#x= 134/41#

#y=169/41#