y2 + 27y = y(y + 27)To factorise you need to find the common factor between each part of the equation. In this case y is common between the different parts of the equation. Therefore you take y outside of the brackets. What is left in the brackets is the rest of each part of the equation: y multiplied by y is y2. y multiplied by 27 is 27y. Therefore you get y2 + 27y.w9/w4 = w5To simplify you need to apply the indices rules. When a letter to a power is divided by the same letter to another power, the indices are subtracted from each other. The indice below is subtracted from the one above.