若函数f(x)定义域为[-1,1],求y=f(x+1/4)*f(x-1/4)的定义域
因为f(x)定义域为[-1,1],所以-1<=x<=1
对f(x+1/4)来说,设x+1/4=t
因为f(t)的定义域是-1<=t<=1
所以
-1<=(x+1/4)<=1
-5/4<=x<=3/4
同理
对(x-1/4)来说
-1<=(x-1/4)<=1
-3/4<=x<=5/4
最后取交集
y=f(x+1/4)*f(x-1/4)的定义域[-3/4,3/4]
因为f(x)定义域为[-1,1],所以-1<=x<=1
对f(x+1/4)来说,设x+1/4=t
因为f(t)的定义域是-1<=t<=1
所以
-1<=(x+1/4)<=1
-5/4<=x<=3/4
同理
对(x-1/4)来说
-1<=(x-1/4)<=1
-3/4<=x<=5/4
最后取交集
y=f(x+1/4)*f(x-1/4)的定义域[-3/4,3/4]