Need help - Parabola Question (2 Viewers)

[Avoodibaba]

Ah, studying for midyears and I've just hit a mental blank on one of my questions:

Show that y=mx-2m^2 is tangent to the parabola x^2=8y

I've tried differentiating to find the gradient function, letting x=m and thus finding the equation but that results in the wrong answer :O

Please help

 

[random-1005]

Ah, studying for midyears and I've just hit a mental blank on one of my questions:

Show that y=mx-2m^2 is tangent to the parabola x^2=8y

I've tried differentiating to find the gradient function, letting x=m and thus finding the equation but that results in the wrong answer :O

Please help

y=mx-2m^2
y=x^2/8

set them equal for intersections

ie x^2/8= mx-2m^2

simplify and u get a quadratic, using discriminant b^2-4ac you get it equal to zero, therefore one intersection, therefore tangent

 

[annabackwards]

I hate trying to do things online, so i've scanned my answer. It shows full working out with an explanation, but you'll have to deal with my handwriting XD

The answer is here: tangentanswer.jpg picture by annabackwards - Photobucket

By the way, you don't have to write the words that i did. You can just show that the discriminant is 0, then say therefore 1 point of intersection, then therefore the line is a tangent

 

[random-1005]

I hate trying to do things online, so i've scanned my answer. It shows full working out with an explanation, but you'll have to deal with my handwriting XD

The answer is here: tangentanswer.jpg picture by annabackwards - Photobucket

By the way, you don't have to write the words that i did. You can just show that the discriminant is 0, then say therefore 1 point of intersection, then therefore the line is a tangent

lol your going to lose some marks in the hsc if you dnt improve your writing

 

[oly1991]

her handwriting isn't that bad....trust me ive seen much worse.

 

[annabackwards]

her handwriting isn't that bad....trust me ive seen much worse.

Thanks lol.

I've gotten by so far with no problems XD

 

[oly1991]

Thanks lol.

I've gotten by so far with no problems XD

can you write fast?

 

[gurmies]

I hate trying to do things online, so i've scanned my answer. It shows full working out with an explanation, but you'll have to deal with my handwriting XD

The answer is here: tangentanswer.jpg picture by annabackwards - Photobucket

By the way, you don't have to write the words that i did. You can just show that the discriminant is 0, then say therefore 1 point of intersection, then therefore the line is a tangent

Haha, YAY, your writing resembles mine xD

 

[Avoodibaba]

Thanks everyone for the help, got it done

D'oh, forgot i about the discriminant.

Oh and you're handwiritng is fine, teachers shouldn't take off marks unless it is completely illegible, especially in maths.

Thanks for going to the trouble of scanning it up, I hate writing out maths stuff on the computer aswell :/

 

[annabackwards]

can you write fast?

I'm probably the fastest writer in my grade - for english and modern i always write 2 or 3 pages more than anyone else.

Other people have super neat writing but when they get into exams it becomes worse than mine XD

Haha, YAY, your writing resembles mine xD

*Hi5*

Thanks everyone for the help, got it done

D'oh, forgot i about the discriminant.

Oh and you're handwiritng is fine, teachers shouldn't take off marks unless it is completely illegible, especially in maths.

Thanks for going to the trouble of scanning it up, I hate writing out maths stuff on the computer aswell :/

Hurrah! I heard that if a teacher at the marking centre can't read a student's writing, they have to find another teacher who can :rofl:

And no worries, i was constructively procrastinating by helping you out

 

[GUSSSSSSSSSSSSS]

LOL if it gives you (ANNA AND GURMIES) any consolence the smartest (and best at math) in my year has HORRIBLE handwriting

....but then again his is on the verge of illegible....so that IS a bit of a worry for external exams =S

 

[annabackwards]

LOL if it gives you (ANNA AND GURMIES) any consolence the smartest (and best at math) in my year has HORRIBLE handwriting

....but then again his is on the verge of illegible....so that IS a bit of a worry for external exams =S

Woooooooooooot!

I feel sorry for the english/art/history markers who have to try and decipher handwriting that is worse than mine. They'd have it tough.