先把函数一般式化为含完全平方差的模式, x的系数化为1
如:5x²-50x+63
=5(x²-10x)+63[先把x的系数化为1]
=5(x²-10x+25²-25²)+63
=5[(x-5)²-25²]+63
=5(x-5)²-25²×5+63
=5(x-5)²-3062