A={xllx+3l+lx-4|≤9}:
|x+3|<=9-|x-4|,
平方得x^2+6x+9<=81-18|x-4|+x^2-8x+16,
18|x-4|<=-14x+88,
9|x-4|<=44-7x,
x<=44/7,81(x^2-8x+16)<=1936-616x+49x^2,
32x^2-32x-640<=0,
x^2-x-20<=0,
A={x|-4<=x<=5},
B={xlx=(4t+1)/(t-6)}
x=4+25/(t-6),
B={x|x≠4，x∈R},
∴A∩B={x|-4<=x<4或4
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