（1）x2+4x+2=0
（2）x2-2x-3=0
（3）（x-3）2+2x（x-3）=0
（4）2x2+1=3x．
（1）x2+4x+4=2，
（x+2）2=2，
x+2=±
，2
∴x1=-2+
，x2=-2-2
；2
（2）（x-3）（x+1）=0，
∴x1=3，x2=-1；
（3）（x-3）（x-3+2x）=0，
（x-3）（3x-3）=0，
∴x1=3，x2=1；
（4）2x2-3x+1=0．
a=2，b=-3，c=1．
∴x=
=-(-3)± (-3)2-4×2×1 2×2
，3±1 4
∴x1=1，x2=
．1 2
| 选词填空。 | |
he always takes a map 3______ him because he doesn't know the way very 4______. But he can't find every place on the map because some places are too 5______. Then he has to ask the policeman for 6______ . Yesterday Mr Zhang's watch 7______, and he wanted to buy a new 8______. But he couldn't find a watch shop. He went to a policeman and 9______ the way. The policeman said, "10______ straight and then turn right. It's next to a fruit shop." Mr Zhang thanked the policeman and went to the watch shop. |