Answer
$(2c-1)(2c-5)$
Work Step by Step
By solving using the box method, it makes it a lot easier to determine what numbers are used in the factorization. You place the first term in the upper left-hand corner and the third term in the bottom right-hand corner. Multiply those two terms and write the product off to the side out of the box. You need to find two numbers that have a product of the number calculated in the prior step, but also have a sum of the second term. Put the two values in the remaining openings (one in each) in the box and find the greatest common factor in each row and column:
