Chapter 10 - Section 10.1 - Adding and Subtracting Polynomials - Exercise Set - Page 706: 71

$2^{2}\times a^{4}$

Since we have the equation, $2\times 2\times a\times a\times a\times a$, and we know that using exponents is just repeated multiplication, we can rewrite the expression using exponential (scientific) notation as $2^{2}\times a^{4}$.