比较长,我放在补充里面1.整体代入法:(复杂计算的简单技巧) (1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)= 2.⑴已知:x/12=y/30=z/4,且(x+y+z)=46
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![比较长,我放在补充里面1.整体代入法:(复杂计算的简单技巧) (1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)= 2.⑴已知:x/12=y/30=z/4,且(x+y+z)=46](/uploads/image/z/4027528-64-8.jpg?t=%E6%AF%94%E8%BE%83%E9%95%BF%2C%E6%88%91%E6%94%BE%E5%9C%A8%E8%A1%A5%E5%85%85%E9%87%8C%E9%9D%A21.%E6%95%B4%E4%BD%93%E4%BB%A3%E5%85%A5%E6%B3%95%EF%BC%9A%EF%BC%88%E5%A4%8D%E6%9D%82%E8%AE%A1%E7%AE%97%E7%9A%84%E7%AE%80%E5%8D%95%E6%8A%80%E5%B7%A7%EF%BC%89+%EF%BC%881%EF%BC%8B1%2F2%EF%BC%8B1%2F3%EF%BC%8B1%2F4%EF%BC%89%C3%97%EF%BC%881%2F2%EF%BC%8B1%2F3%EF%BC%8B1%2F4%EF%BC%8B1%2F5%EF%BC%89%EF%BC%8D%EF%BC%881%EF%BC%8B1%2F2%EF%BC%8B1%2F3%EF%BC%8B1%2F4%EF%BC%8B1%2F5%EF%BC%89%C3%97%EF%BC%881%2F2%EF%BC%8B1%2F3%EF%BC%8B1%2F4%EF%BC%89%3D+2.%E2%91%B4%E5%B7%B2%E7%9F%A5%EF%BC%9Ax%2F12%3Dy%2F30%3Dz%2F4%2C%E4%B8%94%EF%BC%88x%EF%BC%8By%EF%BC%8Bz%EF%BC%89%3D46)
比较长,我放在补充里面1.整体代入法:(复杂计算的简单技巧) (1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)= 2.⑴已知:x/12=y/30=z/4,且(x+y+z)=46
比较长,我放在补充里面
1.整体代入法:(复杂计算的简单技巧)
(1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)=
2.
⑴已知:x/12=y/30=z/4,且(x+y+z)=46 求:x,y,z
⑵已知:a/3=b/4=c/5,且a+b-c=4
求:a,b,c
⑶已知:2a/3=3b/4=4c/5,且4a+3b+8c=20 求:a,b,c
比较长,我放在补充里面1.整体代入法:(复杂计算的简单技巧) (1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)= 2.⑴已知:x/12=y/30=z/4,且(x+y+z)=46
1.设(1+1/2+1/3+1/4)=x,(1/2+1/3+1/4)= y
所以:x-y=1
(1+1/2+1/3+1/4)×(1/2+1/3+1/4+1/5)-(1+1/2+1/3+1/4+1/5)×(1/2+1/3+1/4)=
=x(y+1/5)-(x+1/5)y
=xy+1/5x-xy-1/5y
=1/5(x-y)
=1/5
2.(1)设x/12=y/30=z/4=1份,那么x=12(份),y=30(份),z=4(份)
按比例分配
x=46×12/(12+30+4)=12,
y=46×30/(12+30+4)=30,
z=46×4/(12+30+4)=4.
(2)设a/3=b/4=c/5=1(份),那么a=3(份),b=4(份),c=5(份)
a=4×3/(3+4-5)=6,
b=4×4/(3+4-5)=8,
c=4×5/(3+4-5)=10.
(3)2a/3=3b/4=4c/5,由2a/3=4c/5,那么a=6c/5,
由3b/4=4c/5,得b=16c/15.
4a+3b+8c=20
4×6c/5+3×16c/15+8c=20
解得:c=5/4,
那么:a=5/4×6/5=3/2
b=5/4×16/15=4/3.