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Mathematics: Post your doubts here!

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notnek01

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~P!@$m0~ said:
Find the integer values for x which satisfy the inequality. -3 < 2x -1 <= 6.
please tell me explain me how to do this..? :cry:
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-3 < 2x -1 <= 6 --> -2 < 2x <= 7

--> -1 < x <= 3.5

What integers are there between -1 and 3.5 (not including 1)? The only possibilities are 0, 1, 2 and 3.
 
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Kamber Manji

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notnek01 said:
'The angle that AB makes with the x-axis' is the same as 'the angle that AB makes with any line parallel to the x-axis.'

So draw lines east of A and south of B to make a right-angled triangle. Then use trigonometry to find the angle between AB and the east line.
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Thank you
 
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Curtis512

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hey guys. I always get stuck on the last page of paper 4 when it starts talking about nth terms and (n+1)th terms...
anyway u guys know to make it easy???
 
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humdono

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anybody has notes for transformation stastics and matrices need it asap paper is in less than a week
 
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notnek01

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Curtis512 said:
hey guys. I always get stuck on the last page of paper 4 when it starts talking about nth terms and (n+1)th terms...
anyway u guys know to make it easy???
Click to expand...
If you have a sequence e.g. 2, 4, 6, 8, ... that has an nth term then the (n+1)th term is given by the sequence 4, 6, 8, 10, ... (it starts one term after). Similarly, the (n-1)th term gives you the sequence 0, 2, 4, 6, ...

The nth term is a function where the input is the position and the output is the term, so I will write it as f(n )

E.g. 2, 4, 6, 8, ... : The nth term is f(n ) = 2n

Then the (n+1)th term is f(n+1) = 2(n+1) = 2n+2

And the (n-1)th term is f(n-1) = 2(n-1) = 2n-2.

Does this make sense?
 
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Curtis512

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sor
notnek01 said:
If you have a sequence e.g. 2, 4, 6, 8, ... that has an nth term then the (n+1)th term is given by the sequence 4, 6, 8, 10, ... (it starts one term after). Similarly, the (n-1)th term gives you the sequence 0, 2, 4, 6, ...

The nth term is a function where the input is the position and the output is the term, so I will write it as f(n )

E.g. 2, 4, 6, 8, ... : The nth term is f(n ) = 2n

Then the (n+1)th term is f(n+1) = 2(n+1) = 2n+2

And the (n-1)th term is f(n-1) = 2(n-1) = 2n-2.

Does this make sense?
Click to expand...
sort of, but isn't tehre a formula for a quadratic sequence nth term?
 
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notnek01

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ZaqZainab said:
what is a quadratic sequence
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A quadratic sequence is a sequence where the 'second difference' is constant.

E.g. 3, 5, 8, 12, 17, ...

The 'first differences' are 2, 3, 4, 5, ... and the second difference is 1 (constant) so this is a quadratic sequence.

The nth term of a quadratic sequence is always in the form an^2 + bn + c.

a is the second difference divided by 2. You can find b and c by substituting values and solving simultaneous equations (you're not expected to this method for IGCSE but they may guide you through it).

So it is not completely necessary to know the method for finding the nth terms of quadratic sequences but it is useful to know. They might ask you simple ones like 1, 4, 9, 16, ... or 2, 6, 12, 20, ...
 
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