Question

已知f（x）=X²-1，g（X）=根号下X+1，求f（g(x))

Answer 1

首先x>=-1 ,f(g(x))=f(√(x+1))=(√(x+1))^2-1=x+1-1=x

追问

x为什么要大于等于-1

追答

根号下有意义必 x+1>=0 => x>=-1

Answer 2

f（g(x))=(根号下X+1)的平方-1

Answer 3

由复合函数法则可知f(g(x))=x (x≥-1)

Answer 4

好吧...恭喜楼主

Answer 5

f（x）=X²-1，g（X）=√(X+1)
f(g(x))=[g(x)]²-1=x+1-1=x
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