已知y=(1/3)x-1,求(1/3)x^2-2xy+3y^2-2的值
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将{(1/3)x^2-2xy+3y^2-2}乘以3乘以(1/3)得{x^2-6xy+9y-2}乘以(1/3) ={(x-3y)^2-2}乘以(1/3) 又因为y=(1/3)x-1 变形 3y=x-3 将3y=x-3 代人{6(-3y)^2-2}乘以(1/3) {(x-(x-3)^2-2}乘以(1/3) =(9-2)乘以(1/3) =7/3 不懂的可以问我 我每天下午都在