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Find the largest value of yx for pairs of real numbers (x,y) that satisfy (x3)2+(y3)2=6.

 Apr 9, 2019
 #1
avatar+6251 
+3

y=±6(x3)2+3yx=±6(x3)2+3xThe maximum will be when the numerator has a positive signyx=6(x3)2+3xddxyx=3(x1)x2x2+6x3and this clearly equals 0 at x=1

 

The second derivative evaluated at 1 is less than zero so this is a maximum

 

yx=6(13)2+3=3+2

.
 Apr 9, 2019
 #2
avatar+26396 
+5

Find the largest value of
yx
for pairs of real numbers
(x,y)
that satisfy
(x3)2+(y3)2=6.

 

Let OC2=x2c+y2c=32+32=232

 

OT2+r2=OC2OT2+6=232OT2=186=12=34OT=23

tan(C)=ycxc=33tan(C)=1

tan(B)=rOT=623=2323tan(B)=22

tan(A)=tan(B+C)=tan(B)+tan(C)1tan(B)tan(C)=1+22122=2+222=2+222(2+22+2)=(2+2)242=6+422tan(A)=3+22

 

The largest value of yx=tan(A)=3+22

 

laugh

 Apr 9, 2019
 #3
avatar+130466 
+2

That's a pretty unique method, Heureka.....where did you find it  ????

 

 

 

 

cool cool cool

CPhill  Apr 9, 2019
 #4
avatar+26396 
+2

Hallo CPhill,

 

Thank you,

the answer

i found it myself.

 

laugh

heureka  Apr 10, 2019

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