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Mathematics 14 Online
OpenStudy (anonymous):

solve using substitution -x+3y=4 2x-6y=-8

OpenStudy (kc_kennylau):

Make \(x\) the subject of the first equation :)

OpenStudy (anonymous):

would x=3y-4?

OpenStudy (kc_kennylau):

yep, then subst it into the second equation :)

OpenStudy (anonymous):

awesome then when you substitute it do the 6y cancel?

OpenStudy (anonymous):

im stuck at 6y-4-6y=-8

OpenStudy (kc_kennylau):

but it's 3y-4 not 6y-4

OpenStudy (anonymous):

i thought its 2(3y-4)-6y

OpenStudy (kc_kennylau):

oh sorry

OpenStudy (kc_kennylau):

wait

OpenStudy (kc_kennylau):

try multiplying the first equation by \(-2\)

OpenStudy (anonymous):

im confused???? =[

OpenStudy (anonymous):

-2x-6=8?

OpenStudy (kc_kennylau):

uh you missed out the y

OpenStudy (kc_kennylau):

so after multiplying you can see that the first equation is a duplicate of the second equation, so there's only 1 equation at all

OpenStudy (anonymous):

oh yea i see what your talking about!!!!! so it all cancels out?

OpenStudy (kc_kennylau):

if there's only 1 equation but there's two unknowns, there'll be infinitely many answers

OpenStudy (anonymous):

awesome thank you so much!!!!

OpenStudy (kc_kennylau):

no problem :)

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