26
Let Holly’s number be x, then x2 – 20x = 156
Rearrange this to x2 – 20x – 156 = 0 and solve by factorising
(x + 6)(x – 26) = 0 so x = -6 or x = 26, but since Holly is thinking of a positive integer, her number must be 26.
Coltness High School Mathematics
Welcome to Maths!
26
Let Holly’s number be x, then x2 – 20x = 156
Rearrange this to x2 – 20x – 156 = 0 and solve by factorising
(x + 6)(x – 26) = 0 so x = -6 or x = 26, but since Holly is thinking of a positive integer, her number must be 26.