23, 21___31;
2
2
23, 2(1)___3(1); 23, 2(5)___3(5);
23, 2(1)___3(1);
2
2
等式的基本性质2: 等式两边同时乘同一个数(或除以同一个不为0的 数),所得结果仍是等式。ab
acbc, ab c0
cc 不等式的基本性质2:
不等式的两边都乘以(或除以)同一个正数,不等号
的方向_不_变__。
不等式的基本性质3:
不等式的两边都乘以(或除以)同一个负数,不等号
的方向_改_变__。
不等式基本性质2用式子表述为:
如果a>b,且c>0,那么ac>bc, a/c>b/c; 如果a<b,且c>0,那么ac<bc, 不等a式/c基<b本/性c;质3用式子表述为:
如果a>b,且c<0,那么ac<bc, a/c<b/c; 如果a<b,且c<0,那么ac>bc, a/c>b/c;
( 1 )x 5 1
( 2 ) 2 x 3
解:(1)根据不等式的基本性质1,两边都加上5, 得
x15
即
x4
(2)根据不等式的基本性质3,两边都除以-2, 得
3 x
2
1.将下列不等式化成“x>a”或“x<a”的形式:
( 1 )x 1 2 解:
( 2 ) x 5 6
( 3 )1 x 3 2
• 14、Thank you very much for taking me with you on that splendid outing to London. It was the first time that I had seen the Tower or any of the other famous sights. If I'd gone alone, I couldn't have seen nearly as much, because I wouldn't have known my way about.