求助初一的数学题目
来源:百度知道 编辑:UC知道 时间:2024/05/23 13:35:24
因式分解:
25(a+b)²-9(a-b)²
4x²-(x²+1)²
x³-x
-4x³+16x²-16x
(y+2)²+(y+2)(y-6)
3x³-12xy²
化简(m+n)²+(m+n)(m-3n)
[(2x)/(x-1) - x/(x+1)]÷[ 1/(x²-1)]
已知x+y=3,x+3y=1,求3x²+12xy+12y²的值
试说明当n为自然数时,(n+7)²-(n-5)²能被24整除
25(a+b)²-9(a-b)²
4x²-(x²+1)²
x³-x
-4x³+16x²-16x
(y+2)²+(y+2)(y-6)
3x³-12xy²
化简(m+n)²+(m+n)(m-3n)
[(2x)/(x-1) - x/(x+1)]÷[ 1/(x²-1)]
已知x+y=3,x+3y=1,求3x²+12xy+12y²的值
试说明当n为自然数时,(n+7)²-(n-5)²能被24整除
25(a+b)²-9(a-b)²=[5(a+b)]²-[3(a-b)]²=(5a+5b+3a-3b)(5a+5b-3a+3b)
=(8a+2b)(2a+8b)=4(4a+b)(a+4b)
4x²-(x²+1)² =(2x+x²+1)(2x-x²-1)=-(x+1)²(x-1)²
x³-x=x(x²-1)=x(x+1)(x-1)
-4x³+16x²-16x=-4x(x²-4x+4)=-4x(x-2)²
(y+2)²+(y+2)(y-6)=(y+2)(y+2+y-6)=(y+2)(2y-4)=2(y+2)(y-2)
3x³-12xy²=3x(x²-4y²)=3x(x+2y)(x-2y)
化简(m+n)²+(m+n)(m-3n)=(m+n)(m+n+m-3n)=(m+n)(2m-2n)
=2(m+n)(m-n)
[(2x)/(x-1) - x/(x+1)]÷[ 1/(x²-1)]
=[(2x)(x+1)/(x-1)(x+1) - x(x-1)/(x-1)(x+1)]*(x-1)(x+1)
=2x²+2x-x²+x=x²+3x=x(x+3)
已知x+y=3,x+3y=1,求3x²+12xy+12y²的值
3x²+12xy+12y²=3(x²+4xy+4y²)=3(x+2y)²
x+2y=1/2(2x+4y)=1/2[(x+y)+(x+3y)]=1/2(3+1)=2
3x²+12xy+12y²=3*2²=12
试说明当n为自然数时,(n+7)²-(n-5)²能被24整除
(n+7)²-(n-5)