（x^2-2xy+4y^2)(x+2y)-8x(x+y)(x-y) (64a^3-27b^3)\(4a-3b)-(4a+

luzhiling20082022-10-04 11:39:541条回答

（x^2-2xy+4y^2)(x+2y)-8x(x+y)(x-y) (64a^3-27b^3)(4a-3b)-(4a+3b)^2 (x^4-x+1）/（x^2+2x-3)
（x^2-2xy+4y^2)(x+2y)-8x(x+y)(x-y)
(64a^3-27b^3)(4a-3b)-(4a+3b)^2
(x^4-x+1）/（x^2+2x-3)

已提交，审核后显示！提交回复

liang025sc 共回答了15个问题 | 采纳率93.3%: 又做到你的题了
1）(x^2-2xy+4y^2)(x+2y)-8x(x+y)(x-y)
立方和公式：(a+b)(a²-ab+b²)=a³+b³
(x^2-2xy+4y^2)(x+2y)
=(x+2y)[x²-x×2y+(2y)²]
=x³+8y³
8x(x+y)(x-y)
=8x[(x+y)(x-y)]
=8x(x²-y²)
=8x³-8xy²
所以(x^2-2xy+4y^2)(x+2y)-8x(x+y)(x-y)
=x³+8y³-(8x³-8xy²)
= x³+8y³-8x³+8xy²
=-7x³+8xy²+8y³
2）(64a^3-27b^3)(4a-3b)-(4a+3b)^2
立方差公式：a³-b³=(a-b)(a²+ab+b²)
(64a^3-27b^3)(4a-3b)
=[(4a)³-(3b)³]/(4a-3b)
=(4a-3b)[(4a)²+4a×3b+(3b)²]/ (4a-3b)
=[(4a)²+2×4a×3b+(3b)²]-12ab
=(4a+3b)²-12ab
所以(64a^3-27b^3)(4a-3b)-(4a+3b)^2
=(4a+3b)²-12ab-(4a+3b)²
=-12ab
3）(x^4-x+1）/（x^2+2x-3)
题目有没有出错呢?
还是按原来的做
x^4-x+1
=(x^4-2x+1)+x
=[(x^4-2x²+1)+(2x²-2x)]+x
=[(x²-1)²+2x(x-1)]+(x-1)+1
=[(x+1)²(x-1)²+2x(x-1)+(x-1)]+1
=(x-1)[(x+1)²(x-1)+2x+1]+1
=(x-1)(x³-x+x²-1+2x+1)+1
=(x-1)(x³+x²+x)+1
（x^2+2x-3)
=(x+3)(x-1)
所以(x^4-x+1）/（x^2+2x-3)
=【(x-1)(x³+x²+x)+1】/(x+3)(x-1)
=( x³+x²+x )/(x+3)+[1/(x^2+2x-3)]
=(x³+3x²-2x²-6x+7x+21-21) /(x+3)+[1/(x^2+2x-3)]
=x²-2x+7-[21/(x+2)] +[1/(x^2+2x-3)]; 1年前

若x,y为实数,且1\2≤x^2+4y^2≤2,求x^2-2xy+4y^2的最大值和最小值 fengxueyi1年前1: 1973江湖飘共回答了11个问题 | 采纳率81.8%

可设x=rcost,y=(r/2)sint.[1/(√2)≤r≤√2.].则z=x^2-2xy+4y^2=r^2*[2-(sin2t)]/2.显然,（z)min=1/4,(z)max=3.

1年前查看全部

(-x-2y)(x^2-2xy+4y^2) 计算 zgd26741年前1: fsaefesa 共回答了15个问题 | 采纳率93.3%

(-x-2y)(x^2-2xy+4y^2)
=-x^3-8y^3
直接利用a^3+b^3=(a+b)(a^2-ab+b^2)
将a=-x
b=-2y
代入就可以了.

1年前查看全部

A=4x^2-2xy+4y^2,B=3x^2-6xy+3y^2,|x|=3,y^2=16,|x+y|=1.求4A+[（2 A=4x^2-2xy+4y^2,B=3x^2-6xy+3y^2,|x|=3,y^2=16,|x+y|=1.求4A+[（2A-B）-3（A+B）]的值 ellie001年前3: monsoonz 共回答了20个问题 | 采纳率90%

4A+[（2A-B）-3（A+B）]
=4A+[-A-4B]=3A-4B
=3(4x^2-2xy+4y^2)-4(3x^2-6xy+3y^2)
=18xy
,|x|=3,,|x+y|=1,y^2=16
x=3时,y=-4,18xy=-216
x=-3时,y=4,18xy=-216
综上,18xy=-216

1年前查看全部

,若x^2-y^2=0,求分式x^2-3xy+5y^2/3x^2-2xy+4y^2的值 ,若x^2-y^2=0,求分式x^2-3xy+5y^2/3x^2-2xy+4y^2的值 请尽快回答 aa123451年前1: 孤独求友共回答了22个问题 | 采纳率90.9%

x^2-y^2=0
(x+y)(x-y)=0
x=-y或x=y
当x=-y时
x^2-3xy+5y^2/3x^2-2xy+4y^2
=y^2+3y^2+5y^2/3y^2+2y^2+4y^2
=9y^2/9y^2=1
当x=y时,
x^2-3xy+5y^2/3x^2-2xy+4y^2
=y^2-3y^2+5y^2/3y^2-2y^2+4y^2
=3y^2/5y^2
=3/5

1年前查看全部

已知6x^2-xy-15y^2=0(xy≠0),求(x^2-2xy+4y^2)/(2x^2-3xy-3y^2)的值. 已知6x^2-xy-15y^2=0(xy≠0),求(x^2-2xy+4y^2)/(2x^2-3xy-3y^2)的值. 超级超级抄急抄急！！！！！！！！！ hjl86401年前1: 怎么申请共回答了20个问题 | 采纳率80%

已知6x^2-xy-15y^2=0(xy≠0)
(2x+3y)(3x-5y)=0
2x+3y=0或3x-5y=0
(1）2x+3y=0
2x=-3y
x/y=-3/2
(x^2-2xy+4y^2)/(2x^2-3xy-3y^2)的值
=y^2((x/y)^2-2x/y+4)/y^2(2(x/y)^2-3x/y-3)
=((x/y)^2-2x/y+4)/(2(x/y)^2-3x/y-3)
=((-3/2)^2-2*(-3/2)+4)/(2(-3/2)^2-3*(-3/2)-3)
=(9/4+3+4)/(9/2+9/2-3)
=(37/4)/6
=37/24
(2）3x-5y=0
3x=5y
x/y=5/3
(x^2-2xy+4y^2)/(2x^2-3xy-3y^2)的值
=y^2((x/y)^2-2x/y+4)/y^2(2(x/y)^2-3x/y-3)
=((x/y)^2-2x/y+4)/(2(x/y)^2-3x/y-3)
=((5/3)^2-2*(5/3)+4)/(2(5/3)^2-3*(5/3)-3)
=(25/9-10/3+4)/(50/9-5-3)
=(31/9)/(-22/9)
=-31/22

1年前查看全部

计算整式（x^2-2xy+4y^2)(x+2y)-8x(x+y)(x-y)(64a^3-27b^3)\(4a-3b)-( 计算整式 （x^2-2xy+4y^2)(x+2y)-8x(x+y)(x-y) (64a^3-27b^3)(4a-3b)-(4a+3b)^2 (x^4-x+1）/（x^2+2x-3) 小足过河1年前1: cjf10604 共回答了16个问题 | 采纳率87.5%

又做到你的题了
1）(x^2-2xy+4y^2)(x+2y)-8x(x+y)(x-y)
立方和公式：(a+b)(a²-ab+b²)=a³+b³
(x^2-2xy+4y^2)(x+2y)
=(x+2y)[x²-x×2y+(2y)²]
=x³+8y³
8x(x+y)(x-y)
=8x[(x+y)(x-y)]
=8x(x²-y²)
=8x³-8xy²
所以(x^2-2xy+4y^2)(x+2y)-8x(x+y)(x-y)
=x³+8y³-(8x³-8xy²)
= x³+8y³-8x³+8xy²
=-7x³+8xy²+8y³
2）(64a^3-27b^3)(4a-3b)-(4a+3b)^2
立方差公式：a³-b³=(a-b)(a²+ab+b²)
(64a^3-27b^3)(4a-3b)
=[(4a)³-(3b)³]/(4a-3b)
=(4a-3b)[(4a)²+4a×3b+(3b)²]/ (4a-3b)
=[(4a)²+2×4a×3b+(3b)²]-12ab
=(4a+3b)²-12ab
所以(64a^3-27b^3)(4a-3b)-(4a+3b)^2
=(4a+3b)²-12ab-(4a+3b)²
=-12ab
3）(x^4-x+1）/（x^2+2x-3)
题目有没有出错呢?
还是按原来的做
x^4-x+1
=(x^4-2x+1)+x
=[(x^4-2x²+1)+(2x²-2x)]+x
=[(x²-1)²+2x(x-1)]+(x-1)+1
=[(x+1)²(x-1)²+2x(x-1)+(x-1)]+1
=(x-1)[(x+1)²(x-1)+2x+1]+1
=(x-1)(x³-x+x²-1+2x+1)+1
=(x-1)(x³+x²+x)+1
（x^2+2x-3)
=(x+3)(x-1)
所以(x^4-x+1）/（x^2+2x-3)
=【(x-1)(x³+x²+x)+1】/(x+3)(x-1)
=( x³+x²+x )/(x+3)+[1/(x^2+2x-3)]
=(x³+3x²-2x²-6x+7x+21-21) /(x+3)+[1/(x^2+2x-3)]
=x²-2x+7-[21/(x+2)] +[1/(x^2+2x-3)]

1年前查看全部

（x^2-2xy+4y^2)(x+2y)-8x(x+y)(x-y) (64a^3-27b^3)\(4a-3b)-(4a+

共1条回复

相关推荐

大家在问