(x-5)²=x²-10x+25
∵(x-5)²=x²+kx+25
∴k=-10具体点(x-5)²=x²-10x+25∵(x-5)²=x²+kx+25∴x²+kx+25=x²-10x+25∴kx=-10x∴k=-10