They’re complimentary angles (add up to 90)
Answer:

✑ Question :
- Is ( 11 , 9 ) , ( 11 , 5 ) , ( 9 , 3 ) a function ?
No , it's not a function.
✎ Reason :
This is not a function because one element 11 of set A is associated to elements 9 and 5 of set B.
♨ Explore about function :
↪ Function is a special type of relation. It is the refinement of relation. In a relation from A to B , every element of set A should have only one ( distinct ) image in B to be a function. In other words , if no two different ordered pairs have the same first component , then it is a function.
Hope I helped!
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<span>the sum of the first and three times the second is 54.
x + 3y = 54
3y = 54 - x
y= 54 /3 - x / 3 = 18 -x /3
</span>xy = x (18 -x /3) = 18x - x^2 / 3 = - 1/3 x ^ 2 + 18 x
<span>
</span><span>since a<0, it is concave downward, and the vertex is the maximum value. That vertex occurs at x= - b /2a = (-18) / (-2/3) = 12
</span>
<span>The first number is x=12.
The second is y = </span><span>18 -x /3 = 18- 12/ 3 = 18 - 4 = 14 </span>