初二,因式分解化简求值习题 初二因式分解 化简求值练习题、答案 两道 一道也行
\u6c4250\u9053\u521d\u4e8c\u4e0b\u518c\u6570\u5b66\u56e0\u5f0f\u5206\u89e3\u5316\u7b80\u6c42\u503c\u98981.\u5df2\u77e5\uff1ax+y=1,xy=-1/2,\u5229\u7528\u56e0\u5f0f\u5206\u89e3\u6c42\uff1ax(x+y)(x-y)-(x+y)\u7684\u5e73\u65b9\u7684\u503c.
x(x+y)(x-y)-x(x+y)^2
=x(x+y)(x-y-x-y)
=x(x+y)(-2y)
=-2xy(x+y)
=-2*[-1/2]*1
=1
2.\u5df2\u77e5\uff1aa+b+c=11 \u6c422a^2+2b^2+2c^2+4ab+4ac+4bc\u7684\u503c
2a^2+2b^2+2c^2+4ab+4ac+4bc
=2(a+b+c)^2
=2*11^2
=242
3.\uff082000\u4e09\u6b21\u65b9-2*2001\u4e8c\u6b21\u65b9-1999\uff09/2001\u4e09\u6b21\u65b9+2001\u4e8c\u6b21\u65b9-2002
\u8bbe2001\u4e3ax.
\u5219[(x-1)^3-2x^2-x+2]/x^3+x^2-x-1
4.1.2x\u7684\u5e73\u65b9-7xy-22y\u7684\u5e73\u65b9
\uff08\u6ce8\uff1aX^2\u4ee3\u8868X\u7684\u5e73\u65b9\uff09
2x^2-7xy-22y^2=(2x-11y)(x+2y);
5.1999x\u7684\u5e73\u65b9-(1999\u7684\u5e73\u65b9-1)-1999
1999x^2-(1999^2-1)x-1999
=1999x^2-1999^2x+x-1999
=1999x(x-1999)+(x-1999)
=(x-1999)(1999x+1)
6.(x+3)(x\u7684\u5e73\u65b9-1)(x+5)-20
\uff08X+3\uff09\uff08X+1\uff09\uff08X-1\uff09\uff08X+5\uff09-20
\uff08X^2+4X+3\uff09\uff08X^2+4X-5\uff09-20
\uff08X^2+4X\uff09^2-2\uff08X^2+4X\uff09-35
\uff08X^2+4X+5\uff09\uff08X^2+4X-7)
7.\u5df2\u77e5\u4e09\u89d2\u5f62ABC\u7684\u4e09\u904d\u957f\u5206\u522b\u4e3aabc\u8bd5\u5229\u7528\u5206\u89e3\u56e0\u5f0f\u8bf4\u660e\u5f0f\u5b50b\u7684\u5e73\u65b9-a\u7684\u5e73\u65b9+2ac-c\u7684\u5e73\u65b9
b^2-a^2+2ac-c^2=b^2-(a-c)^2=(b+a-c)(b-a+c)(\u5e73\u65b9\u5dee\u516c\u5f0f)
\u56e0\u4e3aa,b,c\u662f\u4e09\u89d2\u5f62\u4e09\u8fb9,\u6839\u636e\u4e24\u8fb9\u4e4b\u548c\u5927\u4e8e\u7b2c\u4e09\u8fb9,\u6240\u4ee5\u4e0a\u5f0f\u662f\u6b63\u6570.
8.\u6c42\u65b9\u7a0b6xy+4x-9y-7=o \u7684\u6574\u6570\u89e3
6xy+4x-9y-7=0
6xy-9y+4x-6-1=0
3y(2x-3)+2(2x-3)=1
(3y+2)(2x-3)=1
\u5f533y+2=0\u65f6,\u65e0\u6574\u6570\u89e3,\u56e0\u4e3a\u6b64\u65f6y\u4e0d\u662f\u6574\u6570\uff1b
\u5f533y+2\u22600\u65f6,2x-3=1/(3y+2)
\u63a5\u4e0b\u6765\u5206\u60c5\u51b5\u8ba8\u8bba\uff1a\u5f53y\u4e3a\u5c0f\u4e8e-1\u7684\u6574\u6570\u65f6\uff08\u5373\u4ece-2\u5f00\u59cb\uff09,\u90a3\u4e483y+22,\u4e5f\u5c31\u662f\u8bf41/(3y+2)\u6b64\u65f6\u4e5f\u4e0d\u53ef\u80fd\u4e3a\u6574\u6570,\u90a3\u4e48\u89e3\u51fa\u7684x\u4e5f\u4e0d\u53ef\u80fd\u4e3a\u6574\u6570,\u6b64\u65f6\u4e5f\u65e0\u6574\u6570\u89e3.
\u5f53y=-1\u65f6,3y+2=-1,\u90a3\u4e481/(3y+2)=-1,\u5373 2x-3=-1,\u5219x=1,\u6240\u4ee5\u6574\u6570\u89e3\u4e3a\uff081,-1\uff09
解(1-1/(x-1))/(x/(x^-1))
=((x-2)/(x-1))/(x/(x+1)(x-1))
=(x-2)/(x-1)*(x+1)(x-1)/x
=(x-2)(x+1)/x
当x=2时，原式=0
x适当的值一定不能是1，-1，0
2.、1/2(x+y+z)方+1/2(x-y-z)(x-y+z)-z(x+y),其中x-y=6,xy=21.要详细步骤
化简得：
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. 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
=20
4. 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
=20
5.1/4(-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
6. 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
=-6
7. (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
=-4
8. 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
9. 、(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(先化简再求值)
[(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
10. 先化简再求值,1/2a-(2a-2/3b^2)+(-3/2a+2b^2)其中a=-2,b=2/3
原式=-3a+8/3b^2
当a=-2，b=2/3时，
原式=6+8/3×(4/9)=194/27
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