Ok so I was given the equation Y= -3X+9
And the question asked what is the maximum value of xy?
This was from one of my math classes at HS. And I got confused.
To get a maximum value of xy, each x and y needs to be the biggest value, which could be intercepts.
X intercept: 3
Y intercept: 9
XY=27
So I thought the answer would be 27 but I did not see this number among answer choices.
Any ideas?
What are your choices?
can’t remember exactly since it was a few days ago.
But it was like 27/2 , 27/4 , 81/4 , 81/2
thanks!
27/4 because first plug in y = -3x +9 into xy to get -3x^2 +9 set equal to and to find max x (since a is negative) use X=-b/2a you get max x = 3/2 plug back into original equation and solve for y and you get 9/2 for y then multiply x times y and get your answer. You are finding where the vertex of xy is basically and then multiplying x and y