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一、精心选一选(每小题3分,共24分)1.下列合并同类项中,错误的个数有( ).①3y-2y=1;②x~2+x~2=x~4;③3mn-3nm=0;④4ab~2-5ab~2=ab~2;⑤3m~2+4m~3=7m~5.A.1个 B.2个 C.3个 D.4个2.一个多项式减去-2x-1等于6x~2+3x-9,则这个多项式是( ).A.6x~2-10 B.6x~2+x-9C.-6x~2-5x+10 D.6x~2+x-103.下列计算中正确的个数有( ).①(a~5)~2=a~7;②(a~5)~2=a~(25);③(a~2)~5=a~(10);④a~5·a~2=a~(10);⑤a~5·a~2=a~7;⑥(a~5)~2=2a~5;⑦x~3·x~3=2x~6;⑧x~2+x~22x~2.
First, carefully selected one election (each small question 3 points, a total of 24 points) 1. The following combination of similar items, the number of errors () .3y-2y = 1; ②x ~ 2 + x ~ 2 = x ~ 4 ; 3mn-3nm = 0; ④4ab ~ 2-5ab ~ 2 = ab ~ 2; ⑤3m ~ 2 + 4m ~ 3 = 7m ~ 5.A.1 B.2 C.3 D.4 2. One The polynomial minus -2x-1 is equal to 6x ~ 2 + 3x-9, then this polynomial is () .A.6x ~ 2-10B.6x ~ 2 + x-9C.-6x ~ 2-5x + 10D. 6x ~ 2 + x-103. The correct number in the following calculation is: ① (a ~ 5) ~ 2 = a ~ 7; ② (a ~ 5) ~ 2 = a ~ A ~ 5 ~ 2 = a ~ 7; ⑥ (a ~ 5) ~ 2 = 2a ~ 5 ⑦x ~ 3 · x ~ 3 = 2x ~ 6; ⑧x ~ 2 + x ~ 22x ~ 2.