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Urgent AS Maths help please !

Please can someone help me with the following question. I urgently need some help. Any help will be appreciated . Thanks in advance.

Find the set of values of the constant a for which the line y = 2 - 5x intersects the curve y = x^2 + ax + 18 at two points.
Original post by Aty100
Please can someone help me with the following question. I urgently need some help. Any help will be appreciated . Thanks in advance.

Find the set of values of the constant a for which the line y = 2 - 5x intersects the curve y = x^2 + ax + 18 at two points.


So you're saying that

ax+5x=5axax + 5x = 5ax

This is FALSE.

If I have a multiples of something, and I add 5 more, then how many do I have in total?

Aside from that, remember that a quadratic equation has 2 solutions if

b24ac>0 b^2 - 4ac > 0
Reply 2
Original post by Aty100
Please can someone help me with the following question. I urgently need some help. Any help will be appreciated . Thanks in advance.

Find the set of values of the constant a for which the line y = 2 - 5x intersects the curve y = x^2 + ax + 18 at two points.


Use the discriminant to set up an inequality and then solve that inequality to find the set of values that a can take.

Remember that if the line intersects at two points, the discriminant is greater than zero.
Reply 3
Original post by Decerto
Use the discriminant to set up an inequality and then solve that inequality to find the set of values that a can take.

Remember that if the line intersects at two points, the discriminant is greater than zero.


Dunno what I'm doing ?
Reply 4
Original post by Aty100
Dunno what I'm doing ?


Make the two equations equal to each other and then rearrange - you did that first, which is correct.

You would get x^2 + (5+a)x + 16 - as the person above mentioned, you aren't multiplying 5x and Ax so you can't get 5Ax!

use those values in b^2 - 4ac > 0

and you should be able to solve it
(edited 8 years ago)
Reply 5
Original post by Decerto
Make the two equations equal to each other and then rearrange - you did that first, which is correct.

You would get x^2 + (5+a)x + 16 - as the person above mentioned, you aren't multiplying 5x and Ax so you can't get 5Ax!

use those values in b^2 - 4ac > 0

and you should be able to solve it


Managed to get the answer, thanks so much

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