异分母分式的加减计算. 1÷(x+2)-2÷(x-2) x-2-x^2÷(x-2) 计算(4/a^2-4)+(1/2-a)
问题描述:
异分母分式的加减计算. 1÷(x+2)-2÷(x-2) x-2-x^2÷(x-2) 计算(4/a^2-4)+(1/2-a)
1÷(x+2)-2÷(x-2)
x-2-x^2÷(x-2)
(4/a^2-4)+(1/2-a)
答
1÷(x+2)-2÷(x-2)
=[(x-2)-2(x+2)]÷[(x+2)(x-2)
=(-x-6)/(x²-4)
x-2-x^2÷(x-2)
=[(x-2)²-x²]÷(x-2)
=(-4x+4)/(x-2)
(4/a^2-4)+(1/2-a)
=[4-(a+2)]/(a²-4)
=(2-a)/(a+2)(a-2)
=-1/(a+2)第三题他们的公分母是什么(4/a^2-4)=4/(a+2)(a-2)(1/2-a)=-1/(a-2)=-(a+2)/(a+2)(a-2)公分母(a+2)(a-2),也就是a²-4(4/a^2-4)+(1/2-a)=4/(a+2)(a-2)-(a+2)/(a+2)(a-2)=[4-(a+2)]/(a+2)(a-2)=(2-a)/(a+2)(a-2)=-1/(a+2)