ï¼3X+2Y)+(4X+3Y)å
¶ä¸X=5,Y+3
解ï¼åå¼=3X+2Y+4X+3Y=7X+5Y
å½X=5,Y=3æ¶
åå¼=5*7+ï¼-3ï¼*5+20
2.(5a^2-3b^2)+(a^2+b^2)-(5a^2+3b^2),å
¶ä¸a=-1,b=1
=5a^2-3b^2+a^2+b^2-5a^2-3b^2
=a^2-5b^2
=(-1)^2-5*1^2
=1-5
=-4
3.2(a^2b+ab^2)-2(a^2 b-1)-2ab^2 -2å
¶ä¸a=-2,b=2
=2a^2b+2ab^2-2a^2b+2-2ab^2-2
=0
1ãå·²ç¥A,Bæ¯æ¹ç¨x^2+2x-5=0ç两个å®æ°æ ¹,
æ±(A^2+2AB+2A)(B^2+2AB+2B)çå¼.
ç±A,Bæ¯æ¹ç¨x^2+2x-5=0ç两个å®æ°æ ¹å¾ï¼
AB=-5ï¼A+B=-2
A^2+2AB+2A)(B^2+2AB+2B)
=ABï¼A+2B+2ï¼ï¼B+2A+2ï¼
=-5ï¼-2+B+2ï¼ï¼-2+A+2ï¼
=-5AB
=25
2ã1/2(x+y+z)æ¹+1/2(x-y-z)(x-y+z)-z(x+y),å
¶ä¸x-y=6,xy=21.è¦è¯¦ç»æ¥éª¤
åç®å¾ï¼
1/2(x+y+z)æ¹+1/2(x-y-z)(x-y+z)-z(x+y)=
1/2[(x+y)æ¹+2z(x+y)+zæ¹]+1/2[(x-y)æ¹-zæ¹]-z(x+y)=
1/2(x+y)æ¹+1/2(x-y)æ¹=xæ¹ï¼yæ¹
ç±x-y=6,xy=21å¾ï¼xæ¹ï¼yæ¹ï¼ï¼x-yï¼æ¹ï¼2xyï¼78
3ãa^2-ab+2b^2=3 æ±2ab-2a^2-4b^2-7çå¼
2ab-2a^2-4b^2-7
=2(ab-a^2-2b^2)-7
=-2(a^2-ab+2b^2)-7
=(-2)*3-7
=-6-7=-13
4ãè¥A=2x^2+3xy-2x-3,B=-x^2+xy+2,ä¸3A+6Bçå¼ä¸xæ å
³ï¼æ±yçå¼
解ï¼
3A+6B=6x^2+9xy-6x-9-6x^2+6xy+12
=15xy-6x+3
=x(15y-6)+3
5ã9x+6x^2 -3(x-2/3x^2).å
¶ä¸x=-2
9x+6x?? -3(x-2/3x??)
=9x+6x??-3x+2x??
=8x??+6x
=8Ã(-2)??+6Ã(-2)
=32-12
=20
6ã1/4(-4x^2+2x-8)-(1/2x-1),å
¶ä¸x=1/2
1/4(-4x??+2x-8)-(1/2x-1)
=-x??+1/2x-2-1/2x+1
=-x??-1
=-(1/2)??-1
=-1/4-1
=-5/4
7ã3x'y-[2x'y-(2xyz-x'z)-4x'z]-xyz,å
¶ä¸x=-2,y=-3,z=1,
:3x'y-[2x'y-(2xyz-x'z)-4x'z]-xyz
=3x'y-2x'y+2xyz-x'z+4x'z-xyz
=x'y-xyz+3x'z
=4*(-3)-2*3*1+3*4*1
=-12-6+12
=-6
8ã(5a^2-3b^2)+(a^2+b^2)-(5a^2+3b^2),å
¶ä¸a=-1,b=1
=5a^2-3b^2+a^2+b^2-5a^2-3b^2
=a^2-5b^2
=(-1)^2-5*1^2
=1-5
=-4
9ã2(a^2b+ab^2)-2(a^2 b-1)-2ab^2 -2å
¶ä¸a=-2,b=2
=2a^2b+2ab^2-2a^2b+2-2ab^2-2
=0
10ã(X-2åä¹1Y-1)(X-2åä¹1Y+1)-(X-2åä¹1Y-1)çå¹³æ¹
å
¶ä¸X=1.7,Y=3.9(å
åç®åæ±å¼)
[(X-2åä¹1Y)-1][(X+2åä¹1Y)+1]-(X-2åä¹1Y-1)å¹³æ¹
=(X+2åä¹1Y)å¹³æ¹-1-(X-2åä¹1Y)å¹³æ¹+2(X-2åä¹1Y)-1
=(X+2åä¹1Y)å¹³æ¹-(X-2åä¹1Y)å¹³æ¹+2(X-2åä¹1Y)-2
=2XY+2X-Y-2
=3.9*2.4+1.4
=10.76
1ãå·²ç¥A,Bæ¯æ¹ç¨x^2+2x-5=0ç两个å®æ°æ ¹,
æ±(A^2+2AB+2A)(B^2+2AB+2B)çå¼.
ç±A,Bæ¯æ¹ç¨x^2+2x-5=0ç两个å®æ°æ ¹å¾ï¼
AB=-5ï¼A+B=-2
A^2+2AB+2A)(B^2+2AB+2B)
=ABï¼A+2B+2ï¼ï¼B+2A+2ï¼
=-5ï¼-2+B+2ï¼ï¼-2+A+2ï¼
=-5AB
=25
2ã1/2(x+y+z)æ¹+1/2(x-y-z)(x-y+z)-z(x+y),å
¶ä¸x-y=6,xy=21.è¦è¯¦ç»æ¥éª¤
åç®å¾ï¼
1/2(x+y+z)æ¹+1/2(x-y-z)(x-y+z)-z(x+y)=
1/2[(x+y)æ¹+2z(x+y)+zæ¹]+1/2[(x-y)æ¹-zæ¹]-z(x+y)=
1/2(x+y)æ¹+1/2(x-y)æ¹=xæ¹ï¼yæ¹
ç±x-y=6,xy=21å¾ï¼xæ¹ï¼yæ¹ï¼ï¼x-yï¼æ¹ï¼2xyï¼78
3ãa^2-ab+2b^2=3 æ±2ab-2a^2-4b^2-7çå¼
2ab-2a^2-4b^2-7
=2(ab-a^2-2b^2)-7
=-2(a^2-ab+2b^2)-7
=(-2)*3-7
=-6-7=-13
4ãè¥A=2x^2+3xy-2x-3,B=-x^2+xy+2,ä¸3A+6Bçå¼ä¸xæ å
³ï¼æ±yçå¼
解ï¼
3A+6B=6x^2+9xy-6x-9-6x^2+6xy+12
=15xy-6x+3
=x(15y-6)+3
5ã9x+6x^2 -3(x-2/3x^2).å
¶ä¸x=-2
9x+6x² -3(x-2/3x²)
=9x+6x²-3x+2x²
=8x²+6x
=8Ã(-2)²+6Ã(-2)
=32-12
=20
6ã1/4(-4x^2+2x-8)-(1/2x-1),å
¶ä¸x=1/2
1/4(-4x²+2x-8)-(1/2x-1)
=-x²+1/2x-2-1/2x+1
=-x²-1
=-(1/2)²-1
=-1/4-1
=-5/4
7ã3x'y-[2x'y-(2xyz-x'z)-4x'z]-xyz,å
¶ä¸x=-2,y=-3,z=1,
:3x'y-[2x'y-(2xyz-x'z)-4x'z]-xyz
=3x'y-2x'y+2xyz-x'z+4x'z-xyz
=x'y-xyz+3x'z
=4*(-3)-2*3*1+3*4*1
=-12-6+12
=-6
8ã(5a^2-3b^2)+(a^2+b^2)-(5a^2+3b^2),å
¶ä¸a=-1,b=1
=5a^2-3b^2+a^2+b^2-5a^2-3b^2
=a^2-5b^2
=(-1)^2-5*1^2
=1-5
=-4
9ã2(a^2b+ab^2)-2(a^2 b-1)-2ab^2 -2å
¶ä¸a=-2,b=2
=2a^2b+2ab^2-2a^2b+2-2ab^2-2
=0
10ã(X-2åä¹1Y-1)(X-2åä¹1Y+1)-(X-2åä¹1Y-1)çå¹³æ¹
å
¶ä¸X=1.7,Y=3.9(å
åç®åæ±å¼)
[(X-2åä¹1Y)-1][(X+2åä¹1Y)+1]-(X-2åä¹1Y-1)å¹³æ¹
=(X+2åä¹1Y)å¹³æ¹-1-(X-2åä¹1Y)å¹³æ¹+2(X-2åä¹1Y)-1
=(X+2åä¹1Y)å¹³æ¹-(X-2åä¹1Y)å¹³æ¹+2(X-2åä¹1Y)-2
=2XY+2X-Y-2
=3.9*2.4+1.4
=10.76
11.ï¼3X+2Y)+(4X+3Y)å
¶ä¸X=5,Y+3
解ï¼åå¼=3X+2Y+4X+3Y=7X+5Y
å½X=5,Y=3æ¶
åå¼=5*7+ï¼-3ï¼*5+20
12.(5a^2-3b^2)+(a^2+b^2)-(5a^2+3b^2),å
¶ä¸a=-1,b=1
=5a^2-3b^2+a^2+b^2-5a^2-3b^2
=a^2-5b^2
=(-1)^2-5*1^2
=1-5
=-4
13.2(a^2b+ab^2)-2(a^2 b-1)-2ab^2 -2å
¶ä¸a=-2,b=2
=2a^2b+2ab^2-2a^2b+2-2ab^2-2
=0
14.2a-ï¼3a-2b+2ï¼+ï¼3a-4b-1) =ï¼ ï¼ï¼a=b=1
=2a-3a+2b-2+3a-4b-1
=ï¼2-3+3ï¼a+ï¼2-4ï¼b+ï¼-2-1ï¼
=2a-2b-3=-3
15.5-(1-x)-1-(x-1ï¼,x=11
=5-1+x-1-x+1
=4
â¢2x-(x+3y)-(-x-y)-(x-y)=ï¼ ï¼
=2x-x+3y+x+y-x+y
=x+5y
a=2,b=4
æ±2(a-b-54)+3(a+b)
=5a+b-108
=5*2+4-108
=-94
a=b=1
æ±a+b-2(a-b+1)
=-a+3b-2
=-1+3-2
=0
26ï¼-(2x2-y2)-[2y2-(x2+2xy)]=______ï¼
27ï¼è¥-3a3b2ä¸5ax-1by+2æ¯å类项ï¼åx=______ï¼y=______ï¼
28ï¼(-y+6+3y4-y3)-(2y2-3y3+y4-7)ï¼______ï¼
29ï¼åç®ä»£æ°å¼4x2-[7x2-5x-3(1-2x+x2)]çç»ææ¯______ï¼
30ï¼2a-b2+c-d3=2a+( )-d3=2a-d3-( )=c-( )ï¼
31ï¼3a-(2a-3b)+3(a-2b)-b=______ï¼
32ï¼åç®ä»£æ°å¼x-[y-2x-(x+y)]çäº______ï¼
33ï¼[5a2+( )a-7]+[( )a2-4a+( )]=a2+2a+1ï¼
34ï¼3x-[y-(2x+y)]=______ï¼
35ï¼åç®|1-x+y|-|x-y|(å
¶ä¸xï¼0ï¼yï¼0)çäº______ï¼
36ï¼å·²ç¥xâ¤yï¼x+y-|x-y|=______ï¼
37ï¼å·²ç¥xï¼0ï¼yï¼0ï¼åç®|x+y|-|5-x-y|=______ï¼
38ï¼4a2n-an-(3an-2a2n)ï¼______ï¼
39ï¼è¥ä¸ä¸ªå¤é¡¹å¼å ä¸-3x2y+2x2-3xy-4å¾
2x2y+3xy2-x2+2xyï¼
åè¿ä¸ªå¤é¡¹å¼ä¸º______ï¼
40ï¼-5xm-xm-(-7xm)+(-3xm)=______ï¼
41ï¼å½a=-1ï¼b=-2æ¶ï¼
[a-(b-c)]-[-b-(-c-a)]ï¼______ï¼
43ï¼å½a=-1ï¼b=1ï¼c=-1æ¶ï¼
-[b-2(-5a)]-(-3b+5c)ï¼______ï¼
44ï¼-2(3x+z)-(-6x)+(-5y+3z)=______ï¼
45ï¼-5an-an+1-(-7an+1)+(-3an)ï¼______ï¼
46ï¼3a-(2a-4b-6c)+3(-2c+2b)=______ï¼
48ï¼9a2+[7a2-2a-(-a2+3a)]=______ï¼
50ï¼å½2y-x=5æ¶ï¼5(x-2y)2-3(-x+2y)-100=______ï¼
ååé¨ããã