help with exam questions (1 Viewer)

[enigma_1]

How do you do these?

For the second one, does the discriminant need to equal zero? If so then I get m=4 and m=-8, what is right?

thanks

 

[Kurosaki]

For the second one, yeah, you let the discriminant equal 0. Both answers are correct- draw a graph.

 

[enigma_1]

Thanks, how do I do the first one?

 

[Makematics]

Thanks, how do I do the first one?

(c) Let x be length of a side. Draw a diagram. Then from given data, (x-9)(x-7)=48
x^2-16x+63=48
x^2-16x+15=0
(x-1)(x-15)=0
x=1 or x=15
but x>9, and hence x=15cm

 

[panda15]

For part d), they touch when they are equal to each other, so replace y with mx-6, so the quadratic becomes:

For tangency, the line can only touch once, ie. One real root, so you let the discriminant equal 0 and solve for m.

 

[enigma_1]

Thanks sooo much guys <3