How do you solve the following system: #x + 8y = 15 , 4x + y = -1 #?
The solution is
See the explanation below.
Call the two equations (1) and (2) as follows to make it easier to explain:
Multiply (1) by 4 and call it (1'):
Subtract (2) from (1') (we are doing this to eliminate
Divide both sides by 31:
#y=61/31 (or 1.97)
Now plug this value back into one of the original equations to find the value of
(too messy for me to do it in fractions, but you're in the UK not the US so you can probably handle decimals. ;-))
(you can test these solutions by plugging both into either of the original equations and ensuring that it's true (i.e. that both sides are equal, within rounding error))