(2) Solution: The original formula = 7x-3z-8y+5z = 7x-8y+(-3+5) = 7x-8y+2z.

(3) Solution: The original formula = x+[3x+1-4+x] = x+3x+1-4+x = (1+3+1) x-3 = 5x-3.

(4) solution: the original formula =x? -Really? -6x？ +9y？ =( 1-6)x？ +(- 1+9)y？ =-5x？ +8y？

2: (1) solution: the original formula =3x-3-x+5=(3- 1)x+2=2x+2 When x=2, the original formula =2*2+2=4+2=6.

(2) Solution: Original formula =2x? -Really? +2y？ -x？ -x？ +2y？ =(2- 1- 1)x？ +(- 1+2+2)y？ =3y？ When x = 15/ 10 1 and y = 1, the original formula =3* 1=3.

3:A-2B=(5x？ y+4xy)-2(-2xy+x？ y)=5x？ y+4xy+4xy-2x？ y=(5-2)x？ y+(4+4)xy=3x？ y+8xy

4:( 10 b+a)-( 10a+b)= 10b+a- 10a-b =( 10- 1)b+( 1- 10)a = 9 b-9a

5. Cotton field 6x+y mu When x= 120 and y=4, the original formula =6* 120+4=720 (mu).

6:2x？ -3xy+y？ 2xy-2x？ +5xy-2y+ 1=(2-2)x？ +(-3-2+5)xy+( 1-2)y+ 1 =-y+ 1

A: Because the result does not contain the X term, the result of the original formula has nothing to do with X..

7: Because the inverse of X is -5, x = 5；; Because 5|m|=0, m = 0；; Because of 2a? B by Power and 7b? Answer? This is a similar term, so y=2.

2x？ 6y？ +m(xy-9y？ )-(3x？ -3xy+7y？ )=2*5? -6*2? +0(5*2-92? )-(3*2? -3*5*2+7*2? )=50-24+0-( 12-30+28)=50-24+0- 12+30-28= 16

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