In maths, f (x) means as a special relationship where every single input has one output.
<u>Step-by-step explanation:</u>
In mathematics, a function is any expression that gives exactly one answer for each particular number. Input is the number provided in the expression, and output is the number obtained from the search or calculation.
In an ordered pair, input’s first number corresponds to the horizontal axis, and output’s second number in the vertical axis. These ordered pairs can then be plotted. Some data on the costs associated with this are called relationships. For example,

It is often written as "f (x)" where x is the input value and
is the output value.
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The answer is D. 9(y + 3) and 27 + 9y because 9(y + 3) when expanded is 9y + 27. I hope this helps!
Sintheta,costheta,tantheta are only positive in quadrant 1
sintheta is only positive in quad2
tantheta is only positive in quad3
costheta is only positive in quad4
Hi there!
x - 3y = 9
x = 9 + 3y
-4x + y = 8
-4(9+3y) + y = 8
-36 - 12y + y = 8
-36 - 11y = 8
-11y = 44
-y = 4
y = -4
x - 3y = 9
x - 3(-4) = 9
x + 12 = 9
x = 21
So, your answers are y = -4 and x = 21.
Hope this helps!