correct answers please; this is a timed test for me

Question

flash243 · Answer

xy=192 ....(1)

x+3y is minimum

f(x) = x+3*192/x
     =x+576/x

f(x) = 0
1-576/x^2=0

x=24

f"(x)= 1152/x^3
f(24) >0

so this is a minima

x=24
y=192/24=8

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