I want to start off by saying that I probably already know the answer to this question from an exercise I didn't even think would exist in my course due to how ridiculously easy it is, but I am beyond sleepy right now and can't force it out of my brain. I'm pulling an all-nighter to finish up some work, and I can no longer think. I've gone mad. I'm aware this is a stupid question. So I'm given the formula d=0.0065v^2 + 0.75v a) (Some long useless info here) basically translates into find d when v is 50 What I did: d=0.0065(50^2) + 0.75(50) d=0.0065(2500) + 37.5 d=16.25 + 37.5 d=53.75 m (The unit is metres according to the question) That's right, right? I.. no longer have the power to check for myself. b) Find v when d is 100 metres 100=0.0065v^2 + 0.75v I uh, don't seem to remember what to do when there are different powers of a variable being added. Look I know this sounds ridiculous, but I need all the help I can get right now. I'm about to collapse. I'm gonna try to proceed: 100=v(0.0065v +0.75) 100/(0.0065v + 0.75) = v Wait what? No, I can't find v in terms of v.. Thanks in advance gyus edit: My bad. I'm aware this should've been in Ask GBAtemp but there would be no spaces between the lines and it all looks squished and uncomfortable to read, so yeah.

My usual policy against giving complete answers is in effect. a) sure. b) Call it a quadratic equation x=(-b+-sqrt(b^2-4ac))/2a 100=0.0065v^2 + 0.75v 0 =0.0065v^2 + 0.75v - 100

Damn...FAST beat me to it >.< But yeah, A is INCORRECT I LIED SORRY and for b just subtract 100 and plug it into the quadratic equation. To expand upon his suggestion, though, here's what the equation should look like: -.75ÂħSQRT.75^2-(4*.0065*-100) ----------------------------------------- 2*.0065

This is just my IGCSE maths course, fairly simple. I'm willing to bet this formula isn't real but just made of for the sake of this question. I guess I can type out the entire question for you. Warning: Spoilers inside! The stopping distance d m of a car travelling at v km/h is given by d = 0.0065v2 + 0.75v a) Find the stopping distance of a car travelling at 50 km/h b) Estimate the speed of a car which takes 100 m to stop Thanks a lot FAST6191 and Suprgamr232! But.. hang on, something's not quite right. I know for a fact that the answers PDF provided with my book says the answer is 110 km/h as an estimate. (I don't trust it, it sometimes has a lot of mistakes) Replacing v with 110 in the equation doesn't give me anything close to 100. Either it's another mistake, or I'm just really crapping out at the moment.

I wrote down an answer, then saw it had already been answered. Meh.. no point in writing what has already been written.

B...when I plug in 110 I get 140. So...I think your book is wrong...it's more like... Warning: Spoilers inside! 78.46 WARNING: DON'T LOOK IN THE SPOILERS IF YOU DON'T WANT THE ANSWERS