Question 987834


A function is a relation (so, it is the set of ordered pairs) that does not contain two pairs with the same first component.

{{{3x+7y=21 }}}
{{{7y=-3x+21 }}}
{{{y = (-3/7)x +3 }}} defines a function since we can easily find the output {{{y}}} when the input, {{{x}}}, is given. 
If {{{x=1}}}, then {{{y = (-3/7)*1 +3 }}}=>{{{y = -3/7 +21/7=18/7 }}} for example.

Or, if {{{x=7}}}, then {{{y = (-3/7)*7 +3 }}}=>{{{y = -3 +3=0 }}}.

So every {{{x}}} has a corresponding {{{y}}} value.


{{{ graph( 600,600, -10,10, -10, 10, (-3/7)x +3) }}}