17/06/05 02:11:33.74 7CWEzkHb.net
expand[ {x,y}. {{1,1},{-1,1}}.{{2,0},{0,1}}.{{1,-1},{1,1}} .{x,y}/2 ]
expand[2*(x-y)**2/2+1*(x+y)**2/2]
parametricplot[ {cos[s+Pi/4]/sqrt[cos[s]^2/4+sin[s]^2],sin[s+Pi/4]/sqrt[cos[s]^2/4+sin[s]^2]},{s,0,6}]
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polarplot[ 1/sqrt[3/2-cos[s] sin[s]], {s,0,6}]