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3/4x+1/8x=7/8=?

1/2X4+1/4X6+1/6X8+1/8X10+1/10X12 =(1/2-1/4+1/4-1/6+1/6-1/8+1/8-1/10+1/10-1/12)÷2 =(1/2-1/12)÷2 =5/12÷2 =5/24

4.96+1.5x=7.21 1.5x=7.21-4.96 1.5x=2.25 x=2.25/1.5 x=1.5 10.4x-8x=7.2 2.4x=7.2 x=7.2/2.4 x=3 (x+3.3)÷8=2.5 x+3.3=2.5*8 x=20-3.3 x=16.7 谢谢,请采纳

1/[n×(n+1)]=1/n-1/(n+1) ∴原式=(1/3-1/4)+(1/4-1/5)+(1/5-1/6)+(1/6-1/7)+(1/7-1/8)+(1/8-1/9) =1/3-1/9 =2/9

1×2+2×3+...+8×9 太长了,就不抄全了。 =1×(1+1)+2×(2+1)+...+8×(8+1) =1²+2²+...+8²+1+2+...+8 =8×9×17/6 +8×9/2 =204+36 =240 利用公式: 1+2+...+n=n(n+1)/2 1²+2²+...+n²=n(n+1)(2n+1)/6

2x+3=x-1 2x-x=-1-3 x=-4 8x-2=7x-2 8x-7x=-2+2 x=0 10y+7=12y-5-3y 10y+7=9y-5 10y-9y=-5-7 y=-12 2.4x-9.8=1.4x-9 2.4x-1.4x=9.8-9 x=0.8 0.48x-6= -0.02x 0.48x+0.02x=6 0.5x=6 x=12 2x:3=6:5 2x*5=3*6 10x=18 x=1.8 8:3=4x:7 4x*3=7*8 12x=5...

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因为an=n*(n-1)/n+1 所以每个数可以看成2/3+(1+2/4)+(2+2/5)+(3+2/6)...+(8+2/11)= 1+2+3...+8+2/3+2/4+2/5...+2/11=36+2*(1/3+1/4+1/5+...1/11) 因为后面的那个是一个发散数列,好像没有求和公式,所以只能同分计算,当然可以把简单...

=(1-6)X(1-15)X(1-27/2)X(1-63/5)X(1-4)X(1-27/7)X(1-15/4)X(1-11/3) =5X14X(1-27/2)X(1-63/5)X3X(1-27/7)X(1-15/4)X(1-11/3) =5X(1-63/5)X2X(1-27/2)X7X(1-27/7)X3X(1-11/3)X(1-15/4) =(-58)X(-25)X(...

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