y=-1/4x²+3/2x+4
=-1/4(x²-6x)+4
=-1/4(x-6x+9)+9/4+4
=-1/4(x-3)²+25/4为什么后面要加9/4？不是加9吗？难道要乘-1/4吗？括号外面还要乘以-1/4
y=-1/4x²+3/2x+4
=-1/4(x²-6x)+4
=-1/4(x²-6x+9-9)+4
=-1/4(x-6x+9)+9/4+4
=-1/4(x-3)²+25/4