139x137/138+137x1/138奥数减算：1993x1994-1/1993+1992x1994

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139x137/138+137x1/138奥数减算：1993x1994-1/1993+1992x1994
139x137/138+137x1/138
奥数减算：1993x1994-1/1993+1992x1994

139x137/138+137x1/138奥数减算：1993x1994-1/1993+1992x1994
139x137/138+137x1/138
=(138+1)x(138-1)/138+137x1/138
=(138^2-1)/138+137x1/138
=138^2/138+(137-1)/138
=138+136/138
=138+68/69
=138又69分之68
1993x1994-1/1993+1992x1994
分子=1993x(1993+1)-1
=1993^2+1993-1
=1993^2+1992
分母=1993+(1993-1)x(1993+1)
=1993+1993^2-1
=1993^2+1992
所以1993x1994-1/1993+1992x1994=1

139x137/138+137x1/138
=(138+1)x(138-1)/138+137x1/138
=(138^2-1)/138+137x1/138
=138^2/138+(137-1)/138
=138+136/138
=138+68/69
=138又69分之68
1993x1994-1/1993+1992x1994
分子=1...

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139x137/138+137x1/138
=(138+1)x(138-1)/138+137x1/138
=(138^2-1)/138+137x1/138
=138^2/138+(137-1)/138
=138+136/138
=138+68/69
=138又69分之68
1993x1994-1/1993+1992x1994
分子=1993x(1993+1)-1
=1993^2+1993-1
=1993^2+1992
分母=1993+(1993-1)x(1993+1)
=1993+1993^2-1
=1993^2+1992
所以1993x1994-1/1993+1992x1994=1

收起

(1)139X137/138+137/138=(139+1)x137/138
=140x137/138=140x(1-1/138)=140-140/138
=138又68/69
(2)原式=1993x1994-1/1993+1993x1993-1
=1993x1994-1993x1993-1/1993-1
=1993x(1994-1993)-1/1993-1
=1993-1/1993-1
=1991又1992/1993

139x137/138—137x1/138 139X137/138-137X1 1/138 简算;139X137/138-137X1/138急 139x137/138+137x1/138的简便运算 答案上是275又68/69 139x137/138+137x1/138奥数减算：1993x1994-1/1993+1992x1994 计算：139x137/138+137x139/138 139x137/138+137x1又1/138的简便运算 答案上是275又68/69 1.10/7x(200/13-20/11)x0.7x143/5 2.(204+584x1991/1992x584-380)-5/89 3.139x137/138+137x1/1384.已知S=（1/3+1/5+1/7+1/11+1/13)X50055.199又1/9X1/8+599又1/7X1又1/6-201又1/9X9/10-601又1/7X7/8 MATLAB方程求解 范围中所有解目标函数是f(x)=x1+x2+x3+x4+x5+x6+x7+x8+x9还有个约束条件是x1-x9的范围x1>=61;x2>=35;x3>=139;x4>=69;x5>=37;x6>=35;x7>=13;x8>=21;x9>=20;x1给出正解的， 设x1,x2(x1 已知x1,x2(x1 已知x1、x2（x1 若x1,x2(x1 若x1,x2(x1 若x1,x2(x1 已知x1,x2(x1 人教版六年级数学基础训练第10页小探究第二题简便计算下面两题(1) 1X1/2＋1/2X1/3＋1/3X1/4＋1/4X1/5＋1/5X1/6＋1/6X1/7(2) （1/4X1/7＋1/7X1/10＋1/10X1/13＋1/13X1/16)X3现在就要! 用初等行变换来解下列线性方程组（1）2x1-x2+3x3=3 3x1+x2-5x3=0 4x1-x2+x3=3 x1+3x2-13x3=-6(2) x1-2x2+x3+x4=1 x1-2x2+x3-x4=-1 x1-2x2+x3-5x4=5(3) x1-x2+x3-x4=1 x1-x2-x3+x4=0 x1-x2-2x3+2x4=-1/2