1/4x5+1/5x6+1/6x7+.+1/39x40
1个回答
原式=1/4-1/5+1/5-1/6+.+1/39-1/40
=1/4-1/40
=9/40
相关问题
1/(4×5)+1/(5x6)+1/(6x7)……1/(39x40) 有什么简便算法 .
1/2X1/3-1/3X1/4-1/4X1/5-1/5X1/6.1/39X1/40
1/2X1/3-1/3X1/4-1/4X1/5-1/5X1/6.-1/39X1/40
1/1x2x3x4+1/2x3x4x5+1/3x4x5x6+1/4x5x6x7+1/5x6x7x8+1/6x7x8x9+
1.4Y=X 5X+6Y=39
1/4x-1/2=3/4;7x-5/4=3/8;2x-1/6=5x+1/8;1/2x-7=9x-2/6;1/5x-1/2
解方程①5x-1.2=1.8②1.7+7.8-x=5.6③6.4x-x=32.4.
(6x-1/5)-1=5x-7/6
2道容易解方程.1分之9X+5=5X-39 6X-40=4X-24
解方程:(1)6(12x-4)+2x=7-(13x-1)(2)[x-3/0.5-x+40.2=1.6