作业帮初一数学计算,详细步骤!
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初一数学计算,详细步骤!
初一数学计算,详细步骤!
初一数学计算,详细步骤!
一、100²/(252²-248²)
=100²/[(252-248)×(252+248)]
=10000/(4×500)
=10000/2000
=5
二、c
三、（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)
=(1/2)*(3/2)*(2/3)*(4/3)*(3/4)*(5/4)*……*(100/99)*(99/100)*(101/100)
=(1/2)*(101/100)
=101/200
四、因为X²-Y²
=(x+y)(x-y)
所以12=2(x+y)
x+y=6
五、=2*(1-1/2)(1+1/2)(1+1/2^2)(1+1/2^4)(1+1/2^8)+1/2^15
=2*(1-1/2²)(1+1/2²)(1+1/2^4)(1+1/2^8)+1/2^15
=2*(1-1/2^4)(1+1/2^4)(1+1/2^8)+1/2^15
=2*(1-1/2^8)(1+1/2^8)+1/2^15
=2(1-1/2^16)+1/2^15
=2-1/2^15+1/2^15
=2
六、∵a²-3a-1=0
∴a-3-1/a=0
∴a-1/a=3
∴(a+1/a)²
=a²+2+1/a²
=(a²-2+1/a²)+4
=(a+1/a)²+4
=3²+4
=9+4
=13