electrolysis
congenital schmuck
- Joined
- Feb 6, 2008
- Messages
- 1,737
- Gender
- Male
- HSC
- 2009
OMFG ARE YOU SERIOUS?!?!?!Gradient of RO = 1.2, which passes through (0,0)
y = ax^2 + bx
dy/dx = 2ax + b
at x = 0, m = 1.2
therefore, 1.2 = 2(a)(0) + b
b = 1.2
Gradient of QP = -1.8, and P is (30, y)
at x = 30, m = -1.8
therefore, -1.8 = 2(a)(30) + 1.2
-3 = 60a
a = - 1/20
a = -1/20
b = 1.2
ii) Equation is now: y = (-1/20)x^2 + 1.2x
vertex X = -b/2a
= 12
sub that into equation, y = 7.2
thus, v(12, 7.2)
now the distance D = vertical height from vertex to x-axis + height from x axis to Y coordinate of P
We know that P(30, y), sub 30 into the equation and you get -9
therefore P(30, -9)
D = 7.2 + 9
= 16.2
I got part i, then didn't do part ii cause I thought part i was wrong >.>
fml. just lost an easy 2 marks