solve equation, by making appropriate substitution. 

Rule: let U equal the variable part of the second term (without the coefficient)
Then U² will equal the variable part of the first term (without the coefficient)

a)

, which you see is the variable part of the second term

, which is the variable part of the first term 

 becomes




,  
,   

Now substitute back, using ,

,  

Use the definition of a negative exponent to rewrite those:

,  

, 

Cross multiply:

, 

, 

===================================
    
b)
,  the variable part of the second term
,  the variable part of the first term 

 becomes




,  
,   

Now substitute back, using ,

,  

Use the definition of a fractional exponent to rewrite those:

,  

Cubing both sides of both equations:

, 

, 

Edwin