题目内容
解方程.
(1)4x+3×0.7=6.5;
(2)2×(x-0.5)=1.6;
(3)3x×2.34=4.914;
(4)1.44÷x=0.4.
(1)4x+3×0.7=6.5;
(2)2×(x-0.5)=1.6;
(3)3x×2.34=4.914;
(4)1.44÷x=0.4.
分析:(1)原式变为4x+2.1=6.5,根据等式的性质,两边同减去2.1,再同除以4即可;
(2)原式变为2x-1=1.6,根据等式的性质,两边同加上1,再同除以2即可;
(3)原式变为7.02x=4.914,根据等式的性质,两边同除以7.02即可;
(4)根据等式的性质,两边同乘x,得0.4x=1.44,根据等式的性质,两边同除以0.4即可.
(2)原式变为2x-1=1.6,根据等式的性质,两边同加上1,再同除以2即可;
(3)原式变为7.02x=4.914,根据等式的性质,两边同除以7.02即可;
(4)根据等式的性质,两边同乘x,得0.4x=1.44,根据等式的性质,两边同除以0.4即可.
解答:解:(1)4x+3×0.7=6.5
4x+2.1=6.5
4x+2.1-2.1=6.5-2.1
4x=4.4
4x÷4=4.4÷4
x=1.1
(2)2×(x-0.5)=1.6
2x-1=1.6
2x-1+1=1.6+1
2x=2.6
2x÷2=2.6÷2
x=1.3
(3)3x×2.34=4.914
7.02x=4.914
7.02x÷7.02=4.914÷7.02
x=0.7
(4)1.44÷x=0.4
1.44÷x×x=0.4×x
0.4x=1.44
0.4x÷0.4=1.44÷0.4
x=3.6
4x+2.1=6.5
4x+2.1-2.1=6.5-2.1
4x=4.4
4x÷4=4.4÷4
x=1.1
(2)2×(x-0.5)=1.6
2x-1=1.6
2x-1+1=1.6+1
2x=2.6
2x÷2=2.6÷2
x=1.3
(3)3x×2.34=4.914
7.02x=4.914
7.02x÷7.02=4.914÷7.02
x=0.7
(4)1.44÷x=0.4
1.44÷x×x=0.4×x
0.4x=1.44
0.4x÷0.4=1.44÷0.4
x=3.6
点评:此题考查了运用等式的性质解方程,即等式两边同加上或同减去、同乘上或同除以一个数(0除外),两边仍相等,同时注意“=”上下要对齐.
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