How many twin functions are there with y = 2x & sup2; + 1 and range {3,19}? If a series of functions have the same analytic expression, the same range of values, but different domain of definitions, then these functions are "twin functions" Can you make it clear?

+1 -1 +-1
+3 -3 +-3
3*3=9
+-1 and + - 3 correspond to 3 and 19 respectively, with at least one of them
There are three possibilities of + 1 - 1 + - 1 for 1
Similarly, there are three possibilities
There are 3 * 3 = 9 possibilities

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