题目内容
简便计算及解方程
222×999+333×334 | 45×99 | 3(x+2)÷5=(x+2) | ||||||
3(x+1)÷(2x-4)=6 | 7×( x-2 )=2x+3 |
|
分析:(1)根据乘法分配律进行计算;
(2)根据乘法分配律进行计算
(3)等式的两边同时乘上5,然后再进一步解答即可;
(4)等式的两边同时乘上(2x-4),然后再进一步解答即可;
(5)先计算7×( x-2 )=7x-14,然后再进一步解答即可;
(6)等式的两边同时乘上12,然后再进一步解答即可.
(2)根据乘法分配律进行计算
(3)等式的两边同时乘上5,然后再进一步解答即可;
(4)等式的两边同时乘上(2x-4),然后再进一步解答即可;
(5)先计算7×( x-2 )=7x-14,然后再进一步解答即可;
(6)等式的两边同时乘上12,然后再进一步解答即可.
解答:解:(1)222×999+333×334,
=222×(333×3)+333×334,
=666×333+333×334,
=(666+334)×333,
=1000×333,
=333000;
(2)45×99,
=45×(100-1),
=45×100-45×1,
=4500-45,
=4455;
(3)3(x+2)÷5=(x+2),
3(x+2)÷5×5=(x+2)×5,
3(x+2)=(x+2)×5,
3(x+2)-3(x+2)=(x+2)×5-3(x+2),
2(x+2)=0,
2(x+2)÷2=0÷2,
x+2=0,
x+2-2=0-2,
x=-2;
(4)3(x+1)÷(2x-4)=6,
3(x+1)÷(2x-4)×(2x-4)=6×(2x-4),
3(x+1)=6×(2x-4),
3x+3=12x-24,
3x+3-3x=12x-24-3x,
9x-24=3,
9x-24+24=3+24,
9x=27,
9x÷9=27÷9,
x=3;
(5)7×(x-2)=2x+3,
7x-14=2x+3,
7x-14-2x=2x+3-2x,
5x-14=3,
5x-14+14=3+14,
5x=17,
5x÷5=17÷5,
x=3.4;
(6)
-
=
+1,
(
-
)×12=(
+1)×12,
6(2x-1)-4(2x+5)=3(10x-17)+12,
12x-6-8x-20=30x-51+12,
4x-26=30x-39,
4x-26+39=30x-39+39,
4x+13=30x,
4x+13-4x=30x-4x,
26x=13,
26x÷26=13÷26,
x=0.5.
=222×(333×3)+333×334,
=666×333+333×334,
=(666+334)×333,
=1000×333,
=333000;
(2)45×99,
=45×(100-1),
=45×100-45×1,
=4500-45,
=4455;
(3)3(x+2)÷5=(x+2),
3(x+2)÷5×5=(x+2)×5,
3(x+2)=(x+2)×5,
3(x+2)-3(x+2)=(x+2)×5-3(x+2),
2(x+2)=0,
2(x+2)÷2=0÷2,
x+2=0,
x+2-2=0-2,
x=-2;
(4)3(x+1)÷(2x-4)=6,
3(x+1)÷(2x-4)×(2x-4)=6×(2x-4),
3(x+1)=6×(2x-4),
3x+3=12x-24,
3x+3-3x=12x-24-3x,
9x-24=3,
9x-24+24=3+24,
9x=27,
9x÷9=27÷9,
x=3;
(5)7×(x-2)=2x+3,
7x-14=2x+3,
7x-14-2x=2x+3-2x,
5x-14=3,
5x-14+14=3+14,
5x=17,
5x÷5=17÷5,
x=3.4;
(6)
2x-1 |
2 |
2x+5 |
3 |
10x-17 |
4 |
(
2x-1 |
2 |
2x+5 |
3 |
10x-17 |
4 |
6(2x-1)-4(2x+5)=3(10x-17)+12,
12x-6-8x-20=30x-51+12,
4x-26=30x-39,
4x-26+39=30x-39+39,
4x+13=30x,
4x+13-4x=30x-4x,
26x=13,
26x÷26=13÷26,
x=0.5.
点评:四则运算,先弄清运算顺序,然后再进一步计算,能简算的要简算,要根据等式的性质进行解方程.
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简便计算及解方程
222×999+333×334 | 45×99 | 3(x+2)÷5=(x+2) |
3(x+1)÷(2x-4)=6 | 7×( x-2 )=2x+3 | . |