多项式的运算1.X=-2,y=1/2,求(x-2y)(x+2y)-(x-2y²)的值2.解方程:2(x-2)(
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多项式的运算
1.X=-2,y=1/2,求(x-2y)(x+2y)-(x-2y²)的值
2.解方程:2(x-2)(x+3)-(2x-5)(x-1)=3x+7
3.a²+b²+c²=ab+bc+ca.判断a,b,c,的关系
4.化简(1-1/2²)(1-1/3²)(1-1/4²)……(1-1/9²)(1-1/10²)
1.X=-2,y=1/2,求(x-2y)(x+2y)-(x-2y²)的值
2.解方程:2(x-2)(x+3)-(2x-5)(x-1)=3x+7
3.a²+b²+c²=ab+bc+ca.判断a,b,c,的关系
4.化简(1-1/2²)(1-1/3²)(1-1/4²)……(1-1/9²)(1-1/10²)
1.(x-2y)(x+2y)-(x-2y^2)
=x^2-4y^2-x+2y^2
=x^2-x-2y^2
=(-2)^2-(-2)-2*(1/2)^2
=4+2-1/2
=11/2
2.2(x-2)(x+3)-(2x-5)(x-1)=3x+7
2x^2+2x-12-2x^2+7x-5-3x-7=0
6x-24=0
x=4
3.a^2+b^2+c^2=ab+bc+ca
2a^2+2b^2+2c^2=2ab+2bc+2ca
(a^2+b^2-2ab)+(a^2+c^2-2ac)+(b^2+c^2-2bc)=0
(a-b)^2+(a-c)^2+(b-c)^2=0
a-b=0,a-c=0,b-c=0
a=b=c
4.(1-1/2^2)(1-1/3^2)(1-1/4^2)……(1-1/9^2)(1-1/10^2)
=(1+1/2)(1-1/2)(1+1/3)(1-1/3)(1+1/4)(1-1/4)...(1+1/9)(1-1/9)(1+1/10)(1-1/10)
=(3/2)(1/2)(4/3)(2/3)(5/4)(3/4)...(10/9)(8/9)(11/10)(9/10)
=(1/2)(11/10)
=11/20
=x^2-4y^2-x+2y^2
=x^2-x-2y^2
=(-2)^2-(-2)-2*(1/2)^2
=4+2-1/2
=11/2
2.2(x-2)(x+3)-(2x-5)(x-1)=3x+7
2x^2+2x-12-2x^2+7x-5-3x-7=0
6x-24=0
x=4
3.a^2+b^2+c^2=ab+bc+ca
2a^2+2b^2+2c^2=2ab+2bc+2ca
(a^2+b^2-2ab)+(a^2+c^2-2ac)+(b^2+c^2-2bc)=0
(a-b)^2+(a-c)^2+(b-c)^2=0
a-b=0,a-c=0,b-c=0
a=b=c
4.(1-1/2^2)(1-1/3^2)(1-1/4^2)……(1-1/9^2)(1-1/10^2)
=(1+1/2)(1-1/2)(1+1/3)(1-1/3)(1+1/4)(1-1/4)...(1+1/9)(1-1/9)(1+1/10)(1-1/10)
=(3/2)(1/2)(4/3)(2/3)(5/4)(3/4)...(10/9)(8/9)(11/10)(9/10)
=(1/2)(11/10)
=11/20
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