1樓:網際超人
^1、已知a,b是方程x^2+2x-5=0的兩個實數根,
求(a^2+2ab+2a)(b^2+2ab+2b)的值.
由a,b是方程x^2+2x-5=0的兩個實數根得:
ab=-5,a+b=-2
a^2+2ab+2a)(b^2+2ab+2b)
=ab(a+2b+2)(b+2a+2)
=-5(-2+b+2)(-2+a+2)
=-5ab
=252、1/2(x+y+z)方+1/2(x-y-z)(x-y+z)-z(x+y),其中x-y=6,xy=21.要詳細步驟
化簡得:
1/2(x+y+z)方+1/2(x-y-z)(x-y+z)-z(x+y)=
1/2[(x+y)方+2z(x+y)+z方]+1/2[(x-y)方-z方]-z(x+y)=
1/2(x+y)方+1/2(x-y)方=x方+y方
由x-y=6,xy=21得,x方+y方=(x-y)方+2xy=78
3、a^2-ab+2b^2=3 求2ab-2a^2-4b^2-7的值
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
4、若a=2x^2+3xy-2x-3,b=-x^2+xy+2,且3a+6b的值與x無關,求y的值
解: 3a+6b=6x^2+9xy-6x-9-6x^2+6xy+12
=15xy-6x+3
=x(15y-6)+3
5、9x+6x^2 -3(x-2/3x^2).其中x=-2
9x+6x² -3(x-2/3x²)
=9x+6x²-3x+2x²
=8x²+6x
=8×(-2)²+6×(-2)
=32-12
=206、1/4(-4x^2+2x-8)-(1/2x-1),其中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
7、3x'y-[2x'y-(2xyz-x'z)-4x'z]-xyz,其中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
=-68、(5a^2-3b^2)+(a^2+b^2)-(5a^2+3b^2),其中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
=-49、2(a^2b+ab^2)-2(a^2 b-1)-2ab^2 -2其中a=-2,b=2
=2a^2b+2ab^2-2a^2b+2-2ab^2-2
=0 10、(x-2分之1y-1)(x-2分之1y+1)-(x-2分之1y-1)的平方
其中x=1.7,y=3.9(先化簡再求值)
[(x-2分之1y)-1][(x+2分之1y)+1]-(x-2分之1y-1)平方
=(x+2分之1y)平方-1-(x-2分之1y)平方+2(x-2分之1y)-1
=(x+2分之1y)平方-(x-2分之1y)平方+2(x-2分之1y)-2
=2xy+2x-y-2
=3.9*2.4+1.4
=10.76
化間求值: 下面的你自己求吧```
1、-9(x-2)-y(x-5)
(1)化簡整個式子。
(2)當x=5時,求y的解。
2、5(9+a)×b-5(5+b)×a
(1)化簡整個式子。
(2)當a=5/7時,求式子的值。
3、62g+62(g+b)-b
(1)化簡整個式子。
(2)當g=5/7時,求b的解。
4、3(x+y)-5(4+x)+2y
(1)化簡整個式子。
5、(x+y)(x-y)
(1)化簡整個式子。
6、2ab+a×a-b
(1)化簡整個式子。
7、5.6x+4(x+y)-y
(1)化簡整個式子。
8、6.4(x+2.9)-y+2(x-y)
(1)化簡整個式子。
9、(2.5+x)(5.2+y)
(1)化簡整個式子。
10、9.77x-(5-a)x+2a
(5a^2-3b^2)+(a^2+b^2)-(5a^2+3b^2),其中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
=-42(a^2b+ab^2)-2(a^2 b-1)-2ab^2 -2其中a=-2,b=2
=2a^2b+2ab^2-2a^2b+2-2ab^2-2
=0 x+7-(-36+8^2)/2=[-(-8x)+7^4]/3*(8^2-6x)
(a-7)-(-98a)+7a=[(3.2*5a)2^5]/10
(89/2+5x)+35/6x=[3*(-9+5)+2^3]/5+7x
[3x+(-189+5^2)/3]/8=521/2
4y+[119*(-5^3y+8/7)-8/3]=22/11
(3x*189)+
7(2x-1)-3(4x-1)=4(3x+2)-1
(5y+1)+ (1-y)= (9y+1)+ (1-3y)
[-6(-7^4*8)-4]=x+2
20%+(1-20%)(320-x)=320×40%
2(x-2)+2=x+1
2(x-2)-3(4x-1)=9(1-x)
11x+64-2x=100-9x
15-(8-5x)=7x+(4-3x)
3(x-7)-2[9-4(2-x)]=22
3/2[2/3(1/4x-1)-2]-x=2
2x+7^2=157
9x+6x² -3(x-2/3x²)
=9x+6x²-3x+2x²
=8x²+6x
=8×(-2)²+6×(-2)
=32-12
=201/4(-4x²+2x-8)-(1/2x-1)
=-x²+1/2x-2-1/2x+1
=-x²-1
=-(1/2)²-1
=-1/4-1
=-5/4
3.3ab-4ab+8ab-7ab+ab=______.
4.7x-(5x-5y)-y=______.
5.23a3bc2-15ab2c+8abc-24a3bc2-8abc=______.
6.-7x2+6x+13x2-4x-5x2=______.
7.2y+(-2y+5)-(3y+2)=______.
11.(2x2-3xy+4y2)+(x2+2xy-3y2)=______.
12.2a-(3a-2b+2)+(3a-4b-1)=______.
13.-6x2-7x2+15x2-2x2=______.
14.2x-(x+3y)-(-x-y)-(x-y)=______.
16.2x+2y-[3x-2(x-y)]=______.
17.5-(1-x)-1-(x-1)=______.
18.( )+(4xy+7x2-y2)=10x2-xy.
19.(4xy2-2x2y)-( )=x3-2x2y+4xy2+y3.
21.已知a=x3-2x2+x-4,b=2x3-5x+3,計算a+b=______.
22.已知a=x3-2x2+x-4,b=2x3-5x+3,計算a-b=______.
23.若a=-0.2,b=0.5,代數式-(|a2b|-|ab2|)的值為______.
25.一個多項式減去3m4-m3-2m+5得-2m4-3m3-2m2-1,那麼這個多項式等於______.
26.-(2x2-y2)-[2y2-(x2+2xy)]=______.
27.若-3a3b2與5ax-1by+2是同類項,則x=______,y=______.
28.(-y+6+3y4-y3)-(2y2-3y3+y4-7)=______.
29.化簡代數式4x2-[7x2-5x-3(1-2x+x2)]的結果是______.
30.2a-b2+c-d3=2a+( )-d3=2a-d3-( )=c-( ).
31.3a-(2a-3b)+3(a-2b)-b=______.
32.化簡代數式x-[y-2x-(x+y)]等於______.
33.[5a2+( )a-7]+[( )a2-4a+( )]=a2+2a+1.
34.3x-[y-(2x+y)]=______.
35.化簡|1-x+y|-|x-y|(其中x<0,y>0)等於______.
36.已知x≤y,x+y-|x-y|=______.
37.已知x<0,y<0,化簡|x+y|-|5-x-y|=______.
38.4a2n-an-(3an-2a2n)=______.
39.若一個多項式加上-3x2y+2x2-3xy-4得
2x2y+3xy2-x2+2xy,
則這個多項式為______.
40.-5xm-xm-(-7xm)+(-3xm)=______.
41.當a=-1,b=-2時,
[a-(b-c)]-[-b-(-c-a)]=______.
43.當a=-1,b=1,c=-1時,
-[b-2(-5a)]-(-3b+5c)=______.
44.-2(3x+z)-(-6x)+(-5y+3z)=______.
45.-5an-an+1-(-7an+1)+(-3an)=______.
46.3a-(2a-4b-6c)+3(-2c+2b)=______.
48.9a2+[7a2-2a-(-a2+3a)]=______.
50.當2y-x=5時,5(x-2y)2-3(-x+2y)-100=______.
(二)選擇
[ ]a.2;
b.-2;
c.-10;
d.-6.
52.下列各式中計算結果為-7x-5x2+6x3的是 [ ]
a.3x-(5x2+6x3-10x);
b.3x-(5x2+6x3+10x);
c.3x-(5x2-6x3+10x);
d.3x-(5x2-6x3-10x).
53.把(-x-y)+3(x+y)-5(x+y)合併同類項得 [ ]
a.(x-y)-2(x+y);
b.-3(x+y);
c.(-x-y)-2(x+y);
d.3(x+y).
54.2a-[3b-5a-(2a-7b)]等於 [ ]
a.-7a+10b;
b.5a+4b;
c.-a-4b;
d.9a-10b.
55.減去-3m等於5m2-3m-5的代數式是 [ ]
a.5(m2-1);
b.5m2-6m-5;
c.5(m2+1);
d.-(5m2+6m-5).
56.將多項式2ab-9a2-5ab-4a2中的同類項分別結合在一起,應為 [ ]
a.(9a2-4a2)+(-2ab-5ab);
b.(9a2+4a2)-(2ab-5ab);
c.(9a2-4a2)-(2ab+5ab);
d.(9a2-4a2)+(2ab-5ab).
57.當a=2,b=1時,-a2b+3ba2-(-2a2b)等於 [ ]
a.20;
b.24;
c.0;
d.16.
中,正確的選擇是 [ ]
a.沒有同類項;
b.(2)與(4)是同類項;
c.(2)與(5)是同類項;
d.(2)與(4)不是同類項.
59.若a和b均為五次多項式,則a-b一定是 [ ]
a.十次多項式;
b.零次多項式;
c.次數不高於五次的多項式;
d.次數低於五次的多項式.
60.-{[-(x+y)]}+{-[(x+y)]}等於 [ ]
a.0;
b.-2y;
c.x+y;
d.-2x-2y.
61.若a=3x2-5x+2,b=3x2-5x+6,則a與b的大小是
[ ]a.a>b;
b.a=b;
c.a<b;
d.無法確定.
62.當m=-1時,-2m2-[-4m2+(-m2)]等於 [ ]
a.-7;
b.3;
c.1;
d.2.
63.當m=2,n=1時,多項式-m-[-(2m-3n)]+[-(-3m)-4n]等於 [ ]
a.1;
b.9;
c.3;
d.5.
[ ]65.-5an-an-(-7an)+(-3an)等於 [ ]
a.-16an;
b.-16;
c.-2an;
d.-2.
66.(5a-3b)-3(a2-2b)等於 [ ]
a.3a2+5a+3b;
b.2a2+3b;
c.2a3-b2;
d.-3a2+5a-5b.
67.x3-5x2-4x+9等於 [ ]
a.(x3-5x2)-(-4x+9);
b.x3-5x2-(4x+9);
c.-(-x3+5x2)-(4x-9);
d.x3+9-(5x2-4x).
[ ]69.4x2y-5xy2的結果應為 [ ]
a.-x2y;
b.-1;
c.-x2y2;
d.以上答案都不對.
(三)化簡
70.(4x2-8x+5)-(x3+3x2-6x+2).
72.(0.3x3-x2y+xy2-y3)-(-0.5x3-x2y+0.3xy2).
73.-{2a2b-[3abc-(4ab2-a2b)]}.
74.(5a2b+3a2b2-ab2)-(-2ab2+3a2b2+a2b).
75.(x2-2y2-z2)-(-y2+3x2-z2)+(5x2-y2+2z2).
76.(3a6-a4+2a5-4a3-1)-(2-a+a3-a5-a4).
77.(4a-2b-c)-5a-[8b-2c-(a+b)].
78.(2m-3n)-(3m-2n)+(5n+m).
79.(3a2-4ab-5b2)-(2b2-5a2+2ab)-(-6ab).
80.xy-(2xy-3z)+(3xy-4z).
81.(-3x3+2x2-5x+1)-(5-6x-x2+x3).
83.3x-(2x-4y-6x)+3(-2z+2y).
84.(-x2+4+3x4-x3)-(x2+2x-x4-5).
85.若a=5a2-2ab+3b2,b=-2b2+3ab-a2,計算a+b.
86.已知a=3a2-5a-12,b=2a2+3a-4,求2(a-b).
87.2m-{-3n+[-4m-(3m-n)]}.
88.5m2n+(-2m2n)+2mn2-(+m2n).
89.4(x-y+z)-2(x+y-z)-3(-x-y-z).
90.2(x2-2xy+y2-3)+(-x2+y2)-(x2+2xy+y2).
92.2(a2-ab-b2)-3(4a-2b)+2(7a2-4ab+b2).
94.4x-2(x-3)-3[x-3(4-2x)+8].
(四)將下列各式先化簡,再求值
97.已知a+b=2,a-b=-1,求3(a+b)2(a-b)2-5(a+b)2×(a-b)2的值.
98.已知a=a2+2b2-3c2,b=-b2-2c2+3a2,c=c2+2a2-3b2,求(a-b)+c.
99.求(3x2y-2xy2)-(xy2-2x2y),其中x=-1,y=2.
101.已知|x+1|+(y-2)2=0,求代數式5(2x-y)-3(x-4y)的值.
106.當p=a2+2ab+b2,q=a2-2ab-b2時,求p-[q-2p-(p-q)].
107.求2x2-{-3x+5+[4x2-(3x2-x-1)]}的值,其中x=-3.
110.當x=-2,y=-1,z=3時,求5xyz-{2x2y-[3xyz-(4xy2-x2y)]}的值.
113.已知a=x3-5x2,b=x2-6x+3,求a-3(-2b).
(五)綜合練習
115.去括號:{-[-(a+b)]}-{-[-(a-b)]}.
116.去括號:-[-(-x)-y]-[+(-y)-(+x)].
117.已知a=x3+6x-9,b=-x3-2x2+4x-6,計算2a-3b,並把結果放在前面帶「-」號的括號內.
118.計算下式,並把結果放在前面帶「-」號的括號內:
(-7y2)+(-4y)-(-y2)-(+5y)+(-8y2)+(+3y).
119.去括號、合併同類項,將結果按x的升冪排列,並把後三項放在帶有「-」號的括號內:
120.不改變下式的值,將其中各括號前的符號都變成相反的符號:(x3+3x2)-(3x2y-7xy)+(2y3-3y2).
121.把多項式4x2y-2xy2+4xy+6-x2y2+x3-y2的三次項放在前面帶有「-」號的括號內,二次項放在前面帶有「+」號的括號內,四次項和常數項放在前面帶有「-」號的括號內.
122.把下列多項式的括號去掉,合併同類項,並將其各項放在前面帶有「-」號的括號內,再求2x-2[3x-(5x2-2x+1)]-4x2的值,其中x=-1.
123.合併同類項:
7x-1.3z-4.7-3.2x-y+2.1z+5-0.1y.
124.合併同類項:5m2n+5mn2-mn+3m2n-6mn2-8mn.
126.去括號,合併同類項:
(1)(m+1)-(-n+m);
(2)4m-[5m-(2m-1)].
127.化簡:2x2-{-3x-[4x2-(3x2-x)+(x-x2)]}.
128.化簡:-(7x-y-2z)-{[4x-(x-y-z)-3x+z]-x}.
129.計算:(+3a)+(-5a)+(-7a)+(-31a)-(+4a)-(-8a).
130.化簡:a3-(a2-a)+(a2-a+1)-(1-a4+a3).
131.將x2-8x+2x3-13x2-2x-2x3+3先合併同類項,再求值,其中x=-4.
132.在括號內填上適當的項:[( )-9y+( )]+2y2+3y-4=11y2-( )+13.
133.在括號內填上適當的項:
(-x+y+z)(x+y-z)=[y-( )][y+( )].
134.在括號內填上適當的項:
(3x2+xy-7y2)-( )=y2-2xy-x2.
135.在括號內填上適當的項:
(1)x2-xy+y-1=x2-( );
(2)[( )+6x-7]-[4x2+( )-( )]=x2-2x+1.
136.計算4x2-3[x+4(1-x)-x2]-2(4x2-1)的值.
137.化簡:
138.用豎式計算
(-x+5+2x4-6x3)-(3x4+2x2-3x3-7).
139.已知a=11x3+8x2-6x+2,b=7x3-x2+x+3,求2(3a-2b).
140.已知a=x3-5x2,b=x3-11x+6,c=4x-3,求
(1)a-b-c;
(2)(a-b-c)-(a-b+c).
141.已知a=3x2-4x3,b=x3-5x2+2,計算
(1)a+b;
(2)b-a.
142.已知x<-4,化簡|-x|+|x+4|-|x-4|.
146.求兩代數式-1.56a+3.2a3-0.
47,2.27a3-0.02a2+4.
03a+0.53的差與6-0.15a+3.
24a2+5.07a3的和.
-0.3,y=-0.2.
150.已知(x-3)2+|y+1|+z2=0,求x2-2xy-5x2+12xz+3xy-z2-8xz-2x2的值.
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