Exams!!!!

Help!! The exam is in a few days and I’m confused…
This is for the maths as-level exam:
1) The line with equation y = 3x + 1 cut the curve with equation y = x^2 + 4x – 5 at the points A and B. Find the length of AB.
(I found the coordinates A(-3, -8) and B(2, 6) but I don’t know what to do next…)

2) On a journey, the average speed of a car is v m s^-1. For v to be bigger or equal to 5, the cost per kilometre, C pence, of the journey is modelled by: C = 160/v + v^2/100
Using this model,
a) Show, by calculus, that there is a value of v for which C has a stationary value, and find this value of v.
b) Justify that this value of v gives a minimum value of C.
c) Find the minimum value of C and hence find the minimum cost of a 250 km car journey.
(I didn’t even know we DID calculus, whatever it is, is this in the syllabus cuz it’s not in my Edexcel book)

3) Straight line L1 crosses the y-axis with the equation y = 3/2x – 2. The point Q has the coordinates (5, -3). Straight line L2 is perpendicular to L1 and passes through Q.
a) Find the equation for L2 in the form ax + by = c, where a, b and c are integer constants.
Would appreciate any help given .
BB

For question one...you have the co-ordinates....use these to find horizontal and vert distance then use pythagoras' theorum.

Wait for question 2....i haven't read it yet...

G

Thanks for Qs 1....Im so thick

Calculus is differentiation and integration. Surely "stationary value" makes you think of differentiating?

No probs....sometimes i miss the simplest things...and then someone points it out to me...and i feel like a right plonker!

Seriously tho...sometimes your mind gets stuck in one way of doing something...so when the time comes to use a different method...you can't see it! Just take your time when answering questions...and try and look at it from as many different angles (haha..maths pun!!) as possible.

I find that helps loads, hope it helps you.

G

Help!! i have a psychology exam in a few days and i have sooo many names and dates to remember i don't know where to start, any tips would probably save my life!! thanks.