#### Answer

$3^{2}$ * 5

#### Work Step by Step

45
Try to divide 45 by the prime number 3
45 $\div$ 3 = 15
So 15 * 3 =45
Now again divide 15 by the prime number 3
15 $\div$ 3 = 5
45 = 3 *3 * 5
Because all the factors are prime. So the prime factorization of 45 is
3 *3 * 5 = $3^{2}$ * 5