What are the coefficients of the following expression?

For this we almost have an expression of the form:
 ax4 + bx3 + cx2
 Where, the coefficients are given by the values of a, b, c.
 Substituting values we have:
 7x4 - 9x3 + 2x2
 Therefore, the coefficients are:
 a = 7
 b = -9
 c = 2
  
 a = 7 
 b = -9 
 c = 2