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maths question - simultaneous equations

i solved the sim equation but idk how to do part 2.
q3
Reply 1
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No idea, looks way complicated. I've only just finished GCSE maths, and we never did anything like that. Soz.
Reply 3
ik that if a line is a tangent then a 90° is formed meaning that it's perpendicular. do i have to do the same thing that i would do if the question asked me to find the equation of the line tangent to a circle?
Original post by sqrt of 5
i solved the sim equation but idk how to do part 2.
q3

How many times would you expect a line to cut a curve?

0 - they do not interesect
2 - they cross twice
You've found there's just one solution so what does that tell you?
Reply 5
Original post by Muttley79
How many times would you expect a line to cut a curve?

0 - they do not interesect
2 - they cross twice
You've found there's just one solution so what does that tell you?

that the discriminant is equal to 0? idk
Original post by sqrt of 5
that the discriminant is equal to 0? idk


So the line is a t...... to the curve
Reply 7
Original post by Muttley79
How many times would you expect a line to cut a curve?

0 - they do not interesect
2 - they cross twice
You've found there's just one solution so what does that tell you?

ohhhhhhhh now i get it. i need to find the discriminant of the new equation
Reply 8
Original post by sqrt of 5
image-992f1224-bfce-469b-94a3-2cae22a52dfc527161408597682025-compressed.jpg.jpeg
image-d197c418-318e-4b26-8091-aa606c65b2451440818023491435797-compressed.jpg.jpeg

So you have found that there is only one place where the two lines meet (when x=4)

If there were two solutions, the lines would cross twice and if there were no solutions, the lines wouldn't cross at all and there would be no solutions.

Think about what a tangent actually is and you will see how by solving the equation and finding only one solution, y=2x-14 has to be a tangent
Original post by sqrt of 5
ohhhhhhhh now i get it. i need to find the discriminant of the new equation

No - just finding that you have one solution [effectively two equal roots] tells you immediately that its a tangent.
Reply 10
Original post by Muttley79
No - just finding that you have one solution [effectively two equal roots] tells you immediately that its a tangent.


Original post by Savraj11
So you have found that there is only one place where the two lines meet (when x=4)

If there were two solutions, the lines would cross twice and if there were no solutions, the lines wouldn't cross at all and there would be no solutions.

Think about what a tangent actually is and you will see how by solving the equation and finding only one solution, y=2x-14 has to be a tangent

thank youuuuu
Original post by sqrt of 5
thank youuuuu

You would need to write something along the lines of what I've said to explain why the solution you get implies that the line is a tangent.
equate the two equations then simplify into a quadratic, then use the discriminant formula, b^2 -4ac , if your value is negative then the lines dont touch, if your value is 0, then it is a tangent, if your value is greater than 0, then they intersect 2 times

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