Answer:
x² +18x +81
Step-by-step explanation:
(a+b)²=a²+b²+2ab
(x+9)² = x²+9²+2*x*9= x² +18x +81
Answer:

Step-by-step explanation:
1. The situation after 15 min:
(a) Distance travelled by simulated biker:
15 min =¼ h

(b) Distance travelled by Julian
Julian is 2¼ km behind the biker. The distance he has travelled is (5 - 2¼) km
5 - 2¼ = 5 - ⁹/₄ = ²⁰/₄ - ⁹/₄ = ¹¹/₄ = 2¾
Julian has travelled 2¾ km in ¼ h.
2. Julian's average speed
