Need to obtain all marks on this question

Answer:
y = -(8/15)x + 289/15
Step-by-step explanation:
Slope of the normal at P:
(15-0)/(8-0)
15/8
Slope of the tangent:
-8/15
y = (-8/15)x + c
15 = (-8/15)(8) + c
c = 15 + 64/15
c = 289/15
y = -(8/15)x + 289/15