已知二次函数f(x)满足f(x+1)+f(x-1)=2x^2-4x,求f(x)的解析式并求函数的值域.

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已知二次函数f(x)满足f(x+1)+f(x-1)=2x^2-4x,求f(x)的解析式并求函数的值域.
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已知二次函数f(x)满足f(x+1)+f(x-1)=2x^2-4x,求f(x)的解析式并求函数的值域.
已知二次函数f(x)满足f(x+1)+f(x-1)=2x^2-4x,求f(x)的解析式并求函数的值域.

已知二次函数f(x)满足f(x+1)+f(x-1)=2x^2-4x,求f(x)的解析式并求函数的值域.
f(x)=ax²+bx + c
f(x+1) = a(x+1)² + b(x+1) +c = ax² + (2a+b)x + a +b+ c
f(x-1) = a(x-1)² + b(x-1) + c = ax² + (b -2a)x + a -b+ c
f(x+1)+f(x-1) = 2ax² + 2bx + 2(a+c) = 2x² -4x
2a = 2,a = 1
2b = -4,b = -2
a + c = 0,c = -a = -1
f(x) = x² -2x -1 = (x-1)² -2
值域:[-2,∞)