How do you solve this set of linear equations: #7x - 5y = 9; y = x - 1#?

Question

2309 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-11-28T07:08:38

#{(x=2), (y=1) :}#

#{(7x - 5y =9), (y = x - 1) :}#

Substitute #x-1# for #y# in the first equation

#7x - 5(x-1) = 9#

Multiply out the brackets

#7x - 5x + 5 = 9#

Subtract #5# from both sides

#7x -5x = 4#

#2x = 4#

#x = 2#

Then

#y = x - 1#

#y = 2 - 1#

#y = 1#

To check, substitute the answers into the first equation

#7x - 5y = 9#

#14 - 5 = 9#