先化简再求值[(3x-7)]-搜答案-大师作文网

1+(2x-4)/(x^2-a-2)]/[(x+3)/(x^2-1)]={1+2(x-2)/[(x-2)(x+1)]}(x^2-1)/(x+3)=[1+2/(x+1)](x+1)(x-1)/(x+3)

（3x/x-1-x/x+1)*x^2-1/2x,其中x=-3=(3x^2+3x-x^2+1)/(x-1)(x+1)*(x+1)(x-1)/2x=(2x^2+x+1)/2x=x+1/2+1/2x=-3+

=x+(3x-2x)+(5x-4x)+……+(101x-100x)=x+x+……+x=51x=51×2/51=2

3x^3-[-x^2-2(x-x^6)]=3x^3+x^2+2(x-x^6)=3x^3+x^2+2x-2x^6x=-1原式=-3+1-2-2=-6

再问：(x加2）吗？再答：什么？再问：第一个括号里的是x加几

(x-1)(x+2)+(2x-1)(x+5)-3(x的平方-6x-1）=x平方+x-2+2x平方+9x-5-3x平方+18x+3=28x-4=4（7x-1）x=7/228x=14*7=98所以28x-

=[(x+3)(x-3)-7]/(x-3)2(x-3)/(x²-8x+4²)=2(x²-4²)/(x-4)²=2(x+4)(x-4)/(x-4)&su

假如题目没错的话应该是这样首先由3x^2-x=1得x^2=(x+1)/3代入2x^3+7x^2-5x+2009得2x^3+7x^2-5x+2009=2/3x^2-2x+3/7+2009=-16/9x+

[x^2-9]/[x^2+6x+9]】×【[3x^3+9x^2]/[x^2-3x]】=(x+3)(x-3)/(x+3)²*(3x²(x+3)/x(x-3))=(x-3)/(x+3)

∵|x|=3∴x=3或x=-33x²+(2x²-3x)-(-2x+x²)=3x²+2x²-3x+2x-x²=4x²-x当x=3时,

3x^2-[7x^2-2(x^2-3x)-2x]=3x^2-[7x^2-2x^2+6x-2x]=3x^2-[5x^2+4x]=3x^2-5x^2-4x=-2x^2-4x=-2x(-2)^2-4x(-2

5x²-(3y²+5x²)-(4x²+7xy)=5x²-3y²-5x-²4x²-7xy=-4x²-3y

第二题题目不对没有办法做4x^2-2x-1-2(x^2-x-1/2)=4x^2-2x-1-2x^2+2x+1=2x^2当x＝-√5原式=2（-√5）^2=10(9a^2)b-3ab+a^2+(6a^2

(-5x^3-x^2)-(-7x^2+2x^3)=-5x^3-x^2+7x^2-2x^3=-7x³+6x²再问：-3(2a^2-2ab)+4(a^2+ab-6)再答：-3(2a^2

[3x/(x+2)-x/(x-2)]÷2x/(x^2-4)分子分母同时乘以x²-4=[3x(x-2)-x(x+2)]/2x=(3x²-6x-x²-2x)/2x=(2x&#

原式=x²-3x+5当x=-2时y=15

(x-4)(x-2)-(x-1)(x-3)=x²-6x+8-x²+4x-3=-2x+5当x=-5/2时原式=-2*(-5/2)+5=5+5=10

原式=2x²-(7x-4x+3-2x²)=2x²-(3x+3-2x²)=2x²-3x-3+2x²=4x²-3x-3=4×1/4+3

原式=(x+y)(x-y-x+2y)/y=(x+y)y/y=x+y因为已知代数式无意义,即：0的0次方无意义,所以3x-2y-7=0及2x+3y+4=0,解得：x=1,y=-2代入x+y=-1