计算:1²-2²+3²-4²+5²-6²+7²-8²+9²-10²=
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计算:1²-2²+3²-4²+5²-6²+7²-8²+9²-10²=
计算:1²-2²+3²-4²+5²-6²+7²-8²+9²-10²=
计算:1²-2²+3²-4²+5²-6²+7²-8²+9²-10²=
n²-(n+1)²=(n+n+1)(n-n-1)=-(2n+1}
∴1²-2²+3²-4²+5²-6²+7²-8²+9²-10²
=-(2*1+1)-(2*3+1)-(2*5+1)-(2*7+1)-(2*9+1)
=-2(1+3+5+7+9)-5
=-2*25-5
=-55
1-4+9-16+25-36+49-64+81-100=(1+9+25+49+81)-(4+16+36+64+100)=165-240=-75
(1²-2²)+(3²-4²)+(5²-6²)+(7²-8²)+(9²-10²)
= -(1+2)-(3+4)-(5+6)-(7+8)-(9+10)
=-55