Pls, Help! IDK how to do this!

The other factor is (x +3).

Step-by-step explanation:

If the function equals 0, we substitute all the separate factors to 0. We keep the variable on the left side while all the other values go to the right side.x² + 8x + 15 = 0. Here a =1, b =8 and c =15. The product of the factors will equal ac and the sum of the factors will equal b. So the product of factors will equal 15 and the sum of the factors equals 8. The required factors are 5 and 3.     Substituting this, we get x² + 8x + 15 = x² + 3x +5x + 15 = x (x+3) +5(x+5). So the factors are (x+3) and (x+5).