数学简便计算题(平方差公式)
您好:一、(1-1\/2²)(1-1\/3²)(1-1\/4²)……(1-1\/99²)(1-1\/100²)=(1-1\/2)(1+1\/2)(1-1\/3)(1+1\/3)。。。(1-1\/100)(1+1\/100)=1\/2x3\/2x2\/3x...x99\/100x101\/100 =1\/2x101\/100 =101\/200 二、(1+1\/2)(1+1\/2²...
逆用平方差公式计算:(1-1\/2²)(1-1\/3²)(1-1\/4²)...(1-1\/...
解:(1-1\/2²)(1-1\/3²)(1-1\/4²)...(1-1\/10²)=(1+1\/2)(1-1\/2)(1+1\/3)(1-1\/3)...(1+1\/10)(1-1\/10)=(1+1\/2)(1+1\/3)(1+1\/4)..(1+1\/10)(1-1\/2)(1-1\/3)(1-1\/4)...(1-1\/10)=3\/2×4\/3×5\/4×...×11\/...
逆用平方差公式计算:(1-1\/2²)(1-1\/3²)(1-1\/4²)...(1-1\/10&
(1-1\/2²)(1-1\/3²)(1-1\/4²)...(1-1\/10²)=(1+1\/2)(1-1\/2)(1+1\/3)(1-1\/3)...(1+1\/10)(1-1\/10)=(1+1\/2)(1+1\/3)(1+1\/4)..(1+1\/10)(1-1\/2)(1-1\/3)(1-1\/4)...(1-1\/10)=3\/2×4\/3×5\/4×...×11\/10×...
观察: 1-1\/2²=1-1\/4=3\/4=1\/2*2\/3 1-1\/3²=1-1\/9=8\/9=2\/3*4\/3
(1-1\/2²)(1-1\/3²)……(1-1\/2008²)=1\/2*3\/2*2\/3*4\/3*...*2007\/2008*2009\/2008 =1\/2*2009\/2008 =2009\/4016
...1-1\/3²)(1-1\/4²)...(1-1\/99²)(1-1\/100²)
(1-1\/2²)(1-1\/3²)(1-1\/4²)...(1-1\/99²)(1-1\/100²)=(1+1\/2)(1-1\/2)(1+1\/3)(1-1\/3)(1+1\/4)(1-1\/4)...(1+1\/100)(1-1\/100)=3\/2*1\/2*4\/3*2\/3*5\/4*3\/4...101\/100*99\/100 =1\/2*101\/100 =101\/200 ...
(1-1\/2的2次方)(1-1\/3的2次方)(1-1\/4的2次方)..(1-1\/2003的2次方)
计算(1-1\/2²)(1-1\/3²)(1-1\/4²)...(1-1\/2008²)解:原式=(1-1\/2)(1+1\/2)(1-1\/3)(1+1\/3)(1-1\/4)(1+1\/4)...(1-1\/2008)(1+1\/2008)=(1\/2)(3\/2)(2\/3)(4\/3)(3\/4)(5\/4)(4\/5)(6\/5)......
(1-1\/2⊃2;)(1-1\/3⊃2;)(1-1\/4⊃2;)...(1-1\/99⊃2;)(1-1\/10...
(1-1\/2²)(1-1\/3²)(1-1\/4²)...(1-1\/99²)(1-1\/100²=(1-1\/2)(1+1\/2)(1-1\/3)(1+1\/3)(1-1\/4)(1+1\/4)...(1-1\/99)(1+1\/99)(1-1\/100)(1+1\/100)=[(1-1\/2)(1-1\/3)(1-1\/4))...(1-1\/99)(1-1\/100)] * [(...
...1-1\/2²)(1-1\/3²)(1-1\/4²)···(1-\/n²)
:(1-1\/2²)(1-1\/3²)(1-1\/4²)···(1-\/n²)=(1-1\/2)(1+1\/2)(1-1\/3)(1+1\/3)(1-1\/4)(1+1\/4)···(1-1\/n)(1+1\/n)=1\/2×3\/2×2\/3×4\/3×3\/4×5\/4×···×(n-1)\/n×(n+1)\/n =1\/2×(n+1)\/n =(n+1)\/(2n)...
...一减三的平方分之一乘以一减四的平方分之一……一减十平方分之一...
可以利用平方差公式进行简便运算:(1-1\/2²)×(1-1\/3²)×(1-1\/4²)×……×(1-1\/9²)×(1-1\/10²)=(1-1\/2)×(1+1\/2)×(1-1\/3)×(1+1\/3)×(1-1\/4)×(1+1\/4)×……×(1-1\/10)×(1+1\/10)=1\/2×3\/2×2\/3...
利用因式分解计算:(1-1\/2^2)(1-1\/3^2)...(1-1\/9^2)(1-1\/10^2)
(1-1\/2²)(1-1\/3²)(1-1\/4²)...(1-1\/10²)=(1+1\/2)(1-1\/2)(1+1\/3)(1-1\/3)(1+1\/4)(1-1\/4)...(1+1\/10)(1-1\/10) 每个括号内运用平方差公式 =(3\/2)(1\/2)(4\/3)(2\/3)(5\/4)(3\/4)...(11\/10)(9\/10)=[(3\/2)(4\/3)(...