①当y=3x-2时,则代数式3x²-2xy+1/3y²-1的值为多少?②若3的m次方=2,9的n次方=5,则3的2m-4n+1等于多少?
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![①当y=3x-2时,则代数式3x²-2xy+1/3y²-1的值为多少?②若3的m次方=2,9的n次方=5,则3的2m-4n+1等于多少?](/uploads/image/z/1260314-26-4.jpg?t=%E2%91%A0%E5%BD%93y%3D3x-2%E6%97%B6%2C%E5%88%99%E4%BB%A3%E6%95%B0%E5%BC%8F3x%26%23178%3B-2xy%2B1%2F3y%26%23178%3B-1%E7%9A%84%E5%80%BC%E4%B8%BA%E5%A4%9A%E5%B0%91%3F%E2%91%A1%E8%8B%A53%E7%9A%84m%E6%AC%A1%E6%96%B9%3D2%2C9%E7%9A%84n%E6%AC%A1%E6%96%B9%3D5%2C%E5%88%993%E7%9A%842m-4n%2B1%E7%AD%89%E4%BA%8E%E5%A4%9A%E5%B0%91%3F)
①当y=3x-2时,则代数式3x²-2xy+1/3y²-1的值为多少?②若3的m次方=2,9的n次方=5,则3的2m-4n+1等于多少?
①当y=3x-2时,则代数式3x²-2xy+1/3y²-1的值为多少?②若3的m次方=2,9的n次方=5,
则3的2m-4n+1等于多少?
①当y=3x-2时,则代数式3x²-2xy+1/3y²-1的值为多少?②若3的m次方=2,9的n次方=5,则3的2m-4n+1等于多少?
①3x²-2xy+1/3y²-1
=3x²-2x(3x-2)+1/3 (3x-2)²-1
=3x²-6x²+4x+3x²-4x-4/3-1
=-7/3
②3^m=2 9^n=5→3^(2n)=5
3^(2m-4n+1)=3^(2m)÷3^(4n)×3=(3^m)²÷(3^2n)²×3=2²÷5²×3=12/25