We need two numbers whose sum is 20 and product is 100. The numbers 10 and 10 work, so the factors are (x + 10)(x + 10). For a quadratic of the form x² + bx + c, look for two numbers that multiply to c and add to b. Those two numbers become the constants in the two brackets. You can verify the factorization by expanding the brackets and checking that the middle term and constant term are correct. The correct answer is (x + 10)(x + 10), which matches the calculation or reasoning shown.