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if f(x)=x^(3/2)-1, find the inverse solution

 Oct 20, 2014

Best Answer 

 #2
avatar+128707 
+5

Geno's answer is correct, but let me add one proviso.

We must restrict the domain on the inverse to x ≥ - 1.

The reason for this is that if (a,b) is on the inverse graph, then (b, a ) must be on the original graph.  And the minimum point on  y = x^(3/2) - 1 =  (0,-1). Notice that if we put -9 into y = (x + 1)^(2/3), the result is 4.  So the point (-9,4) is on the inverse graph, but the point (4, -9) isn't on the original graph. And notice that if we put -1 into the inverse, it returns 0.  And for all x values greaer than -1 on the inverse, the two graphs will maintain this (a,b), (b,a) relationship.

 

 Oct 20, 2014
 #1
avatar+23247 
+5

f(x)  =  x^(3/2) - 1

y  =  x^(3/2) - 1

Step #1:  interchange x and y:

          x  =  y^(3/2) -1

Step #2:  solve for y:

          x+ 1  =  y^(3/2)

          Square both sides:  (x + 1)^2  =  y^3

          Find the cube root of both sides:  (x + 1) ^(2/3)  =  y

Answer:  y  =  (x + 1) ^(2/3) 

If you have any questions, please post back.

 Oct 20, 2014
 #2
avatar+128707 
+5
Best Answer

Geno's answer is correct, but let me add one proviso.

We must restrict the domain on the inverse to x ≥ - 1.

The reason for this is that if (a,b) is on the inverse graph, then (b, a ) must be on the original graph.  And the minimum point on  y = x^(3/2) - 1 =  (0,-1). Notice that if we put -9 into y = (x + 1)^(2/3), the result is 4.  So the point (-9,4) is on the inverse graph, but the point (4, -9) isn't on the original graph. And notice that if we put -1 into the inverse, it returns 0.  And for all x values greaer than -1 on the inverse, the two graphs will maintain this (a,b), (b,a) relationship.

 

CPhill Oct 20, 2014

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