mitchelsewbaran
If the 2 lines given by the equations 12x+3y=20 and ax+y=10 don't intersect when graphed, what is the value of "a"?



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sasogeek
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if they don't intersect, it means they're parallel and their gradient is the same. find the gradient of the first equation and that's equal to "a" :)

zzr0ck3r
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set both equal to y, and make them have the same slope

zzr0ck3r
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as long as they dont have the same y intercept they will not cross if they have the same slope

zzr0ck3r
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3y = 20 3x
y = x(20/3)
and the other equation set to y is what?

zzr0ck3r
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@mitchelsewbaran ?

mitchelsewbaran
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hmmm.....

zzr0ck3r
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that should be +(20/3)

zzr0ck3r
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y = x+(20/3)

zzr0ck3r
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solve for y in the second equation

zzr0ck3r
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y = ax+10
we want them to have the same slope so what does a need to be?
y = x+(20/3)
y = ax+10
a = ?

mitchelsewbaran
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10?

sasogeek
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12x+3y=20
solve for y
3y=12x+20
y=4x+(20/3)
can u tell what the slope is?

sasogeek
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@mitchelsewbaran ... ?

mitchelsewbaran
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hold on