Which of the following is a true polynomial identity? a. (x^2+1)(x^2-a)= x^4-ab. (x^2+1)(x^2+a)= x^2(x^2+a+1)c. (x^2+1)(x^2+a)-a = x^2(x^2+a+1)d. (x^2+1)(x^2+a)= x^2+ax^2+a

  c.  (x^2+1)(x^2+a)-a = x^2(x^2+a+1)

Step-by-step explanation:

You can use FOIL or the distributive property to expand the product of binomials, Then collect terms and factor out the common factor.

  (x^2+1)(x^2+a)-a

  = x^2(x^2 +a) +1(x^2 +a) -a

  = x^4 +ax^2 +x^2 +a -a

  = x^4 +ax^2 +x^2

  = x^2(x^2 +a +1) . . . . . matches choice C

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