34.將(0,4)代入y=X2次+ax+b

                           4=0的2次方+a(0)+b

                            4=0+a+b

                              b=4

          將士5,9)代入y=x的2次方+ax+b

                                  9=5x5+a(5)+4

                                   9=25+5a+4

                                    9=25+4+5a

                                     9-25=5a

                                     -20=5a

                                          a=-4

x的2次方-4a+4=0

a=1     b=-4      c-4

x=-(-4)+-開方(-4)2次方-4(1)(4)

x=4+-開方0/2

x=2