(2n`2-3n)-[2(n-1)`2-3(n-1)] =4n-5

题目

(2n`2-3n)-[2(n-1)`2-3(n-1)] =4n-5
( 2n`2-3n)-[2(n-1)`2-3(n-1)]
=4n-5
越详细越好,
还有那个2(n-1)`2怎么变化也要详细说明,

答案

(2n²-3n)-[2(n-1)²-3(n-1)]
=(2n²-3n)-[2(n²-2n+1)-3(n-1)]
=(2n²-3n)-[2n²-4n+2-3n+3]
=2n²-3n-2n²+4n-2+3n-3
=4n-5