簡(jiǎn)便計(jì)算及解方程
222×999+333×33445×993(x+2)÷5=(x+2)
3(x+1)÷(2x-4)=67×( x-2 )=2x+3數(shù)學(xué)公式

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)
,
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.
分析:(1)根據(jù)乘法分配律進(jìn)行計(jì)算;
(2)根據(jù)乘法分配律進(jìn)行計(jì)算
(3)等式的兩邊同時(shí)乘上5,然后再進(jìn)一步解答即可;
(4)等式的兩邊同時(shí)乘上(2x-4),然后再進(jìn)一步解答即可;
(5)先計(jì)算7×( x-2 )=7x-14,然后再進(jìn)一步解答即可;
(6)等式的兩邊同時(shí)乘上12,然后再進(jìn)一步解答即可.
點(diǎn)評(píng):四則運(yùn)算,先弄清運(yùn)算順序,然后再進(jìn)一步計(jì)算,能簡(jiǎn)算的要簡(jiǎn)算,要根據(jù)等式的性質(zhì)進(jìn)行解方程.
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簡(jiǎn)便計(jì)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
2x-1
2
-
2x+5
3
=
10x-17
4
+1

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