(5x+1)(5x-1)-5(x+25x²)=(25x²-1)-5(x+25x²)=25x²-1-5x-125x²=-100x²-5x-1=-100×(2/5)²-5×(2/5)-1=-100×(4/25)-5×(2/5)-1=-16-2-1=-19 很高兴为您解答,祝你学习进步!【the 1...