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?

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