How do you solve this set of linear systems: #x- 4y = 8; 2x - y = - 5#?

Answer 1

Eva Adamson

#x = -4# and #y = -3#

Step 1) Solve the first equation for #x#:

#x - 4y + 4y = 8 + 4y#

#x = 8 + 4y#

Step 2) Substitute #8 + 4y# for #x# in the second equation and solve for #y#:

#2(8 + 4y) - y = -5#

#16 + 8y - y = -5#

#16 + 7y = -5#

#16 - 16 + 7y = -5 - 16#

#7y = -21#

#(7y)/7 = (-21)/7#

#y = -3#

Step 3) Substitute #-3# for #y# in the solution in Step 1) and calculate #x#:

#x = 8 + (4*-3)#

#x = 8 - 12#

#x = -4#

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

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