化简求值已知3M N=4x平方-5x
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3m-6n=3(m-2n)m²-4mn+4n²=(m-2n)²m=2,n=3(m-2n)=-4所以3m-6n=-12m²-4mn+4n²=16横线处是
原式=(x³-4x)-(x³-3x²+2x-3x²-9x+6)-(2x²-4x)=x³-4x-x³+7x-6-2x²+4
代数式3x的平方-2x的值是53x^2-2x=56x的平方-4x+5=2(3x^2-2x)+5=2*5+5=15
2(3x的平方+y)-(2x的平方-y)=6x²+2y-2x²+y=4x²+3y=4*(1/2)²+3*(-1)=1-3=-2
X^2+Y^2-4X+6Y+13=0(x-2)^2+(y+3)^2=0x=2,y=-3(3X+Y)^2-3(3X-Y)(X+Y)-(X-3Y)(X+3Y)=9x^2+6xy+y^2-3(3x^2+2x
2(x立方+4x平方-1)-(x-3x平方+2x立方)=2X³+8X²-2-X+3X²-2X³=11X²-X-2当X=-3时,原式=11*(-3)
(1)A+B=4x²-7x+1+2x²+3x-4=6x²-4x-32A+B=2(4x²-7x+1)-(2x²+3x-4)=8x²-14x+2
原式=4(x-y)平方/2(x+y)(x-y)=2(x-y)/x+y=-2/5
解2x²-1/2[6-2(x²-2)]=2x²-3+(x²-2)=(2x²+x²)+(-3-2)=3x²-5=3×(-2)
-(mn-3)+3(-mn-1)-5mn=-mn+3-3mn-3-5mn=-9mn=-9*2*23=-414
解1原式=9X+6X^2-3X+2X^2=8X^2+6X将X=-2代入,得8*4-6*2=32-12=20解2原式=a^2b-ab-ab^2-ab+2ab^2+2ab=a^b+ab^2将a=-1/2b
(4x²-3x)+(2+4x-x²)-(2x²+x+1)先去括号;4x²-3x+2+4x-x²-2x²-x-1合并同类项x²+1代
m平方+n平方-2m-6n+10=0m²-2m+1+n²-6n+9=0(m-1)²+(n-3)²=0由非负性m-1=0n-3=0解得m=1n=3则m平方-2mn
2(x²y+xy)-3(x²y+xy)-4x²y=-(x²y+xy)-4x²y=-5x²y-xy=-xy(5x+1)=1×2(-5+1)=-
X=-1/2Y=-2/3解=-5/9不知道对不对=.=!
合并同类项,再把X=-1/2代入计算即可
2(x的平方+xy)-3(xy的平方-xy)-4x的平方y=2x²+2xy-3xy²+3xy-4x²y=2x²+5xy-xy(3y+4x)
原式=(x+y)(x-y)-(x-y)=(x-y)(x+y-1)(2b-a+m)/2-(1/2b-a+m)=1两边乘22b-a+m-b+2a-2m=2m=b+a-2=-1+3-2=0
【(x的平方+5x+6)/(x+3)/(x平方-4)/(x-3)】-1=【(x+2)(x+3)/(x+3)/(x平方-4)/(x-3)】-1=【(x+2)/(x+2)(x-2)/(x-3)】-1=【1
x+1/x=3等号两边同时平方得:x+1/x=7;代入下式x/(x^4+x+1);分子分母同除以x=1/(x+1+1/x)=1/(7+1)=1/8