f(x,y)=10x5−3x2y6−4y4
Differentiate w.r.t x
f(x,y)x=50x4=6xy6
Again differentiate w.r.t x-
f(x,y)xx=200x3−6y6
f(1,2)xx=200(1)3−6(2)6=200−384=−184
f(1,−2)xx=200(1)3−6(−2)6=200−384=−184
Now differentiate w.r.t y-
f(x,y)y=−18x2y5−16y3
Again differentiate w.r.t. y-
f(x,y)yy=−90x2y4−48y2
f(1,2)yy=−90(1)2(2)4−48(2)2=−1440−192=−1632
f(1,−2)yy=−90(1)2(−2)4−48(−2)2=−1140−192=−1632
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