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# C1 Question Watch

1. Really stuck with this 1 mark question ...

A circle with centre C (-5,6) touches the y axis as shown in the diagram

Find the equation of the circle in the form

i found that out ... ,

BUT the next question says verify that the point P (-2,2) lies on the circle

i dont know how to work it out help pl0x
2. (Original post by Skaterkid)
Really stuck with this 1 mark question ...

A circle with centre C (-5,6) touches the y axis as shown in the diagram

Find the equation of the circle in the form

i found that out ... ,

BUT the next question says verify that the point P (-2,2) lies on the circle

i dont know how to work it out help pl0x
Sub x = -2 and y = 2 into the equation. It lies on the circle if the equation equals 5.
3. (Original post by im so academic)
Sub x = -2 and y = 2 into the equation. It lies on the circle if the equation equals 5.
I expanded the brackets and then subed it LHS is -16 and RHS is -20
4. (Original post by Skaterkid)
I expanded the brackets and then subed it LHS is -16 and RHS is -20
Is the original equation correct?
5. (Original post by Skaterkid)

i found that out ... ,

5 !!!!!!
6. Yes, remember the equation of the circle equals r squared. There is a mistake when you tried to find out the equation of the circle.
7. (Original post by Skaterkid)
I expanded the brackets and then subed it LHS is -16 and RHS is -20
The RHS doesn't equal 20. You've substituted your values in wrong.
8. (Original post by ghostwalker)
5 !!!!!!
Yeah, I was a bit suspicious of that first. Usually the radius squared is square number.
9. (-2+5)^2=9
(2-6)^2=16
=25
10. (Original post by iPthreefifthteen)
(-2+5)^2=9
(2-6)^2=16
=25
11. (Original post by iPthreefifthteen)
(-2+5)^2=9
(2-6)^2=16
=25
Is that the correct method to use in the exams?
12. (Original post by Skaterkid)
Is that the correct method to use in the exams?
It's as good as any

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