FP2 Inequalities. Edexcel (but can be for all)

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ShafTJB
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With FP2, they sometimes ask us to find the solutions to inequalities using alegbraic manipulation. I find it so much easier to first, find the critical values, and then draw the graphs that are intersecting, then follow on to find my inequality from there. So, can this be deemed as algebraic manipulation? Or will I lose the marks. I always use the graph method and it comes out correct all the time.

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lizard54142
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(Original post by ShafTJB)
With FP2, they sometimes ask us to find the solutions to inequalities using alegbraic manipulation. I find it so much easier to first, find the critical values, and then draw the graphs that are intersecting, then follow on to find my inequality from there. So, can this be deemed as algebraic manipulation? Or will I lose the marks. I always use the graph method and it comes out correct all the time.

Thanks.
If it specifically states in the question to use an algebraic method, you should use an algebraic method, otherwise you will lose marks. But if it just says "solve this inequality" or "find the range of values which satisfy..." then any correct, valid method will get full marks.
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maggiehodgson
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(Original post by ShafTJB)
With FP2, they sometimes ask us to find the solutions to inequalities using alegbraic manipulation. I find it so much easier to first, find the critical values, and then draw the graphs that are intersecting, then follow on to find my inequality from there. So, can this be deemed as algebraic manipulation? Or will I lose the marks. I always use the graph method and it comes out correct all the time.

Thanks.
Yes, that's what I've been doing. You have to use algebra for the fist bit anyway don't you. In fact, without the picture at the end I'd be lost. Any clues as to what you should be doing then?
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math42
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They generally expect you to algebraically find all the critical values, but you are then free to obtain the range of values for x however you like. From a 2013 mark scheme (the question asks for you to use algebra):
"using their 4 critical values to obtain appropriate ranges e.g. use a sketch graph of a quartic, (whichmust be the correct shape and cross the x-axis at the cvs) or a table or number line"
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maggiehodgson
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(Original post by 13 1 20 8 42)
They generally expect you to algebraically find all the critical values, but you are then free to obtain the range of values for x however you like. From a 2013 mark scheme (the question asks for you to use algebra):
"using their 4 critical values to obtain appropriate ranges e.g. use a sketch graph of a quartic, (whichmust be the correct shape and cross the x-axis at the cvs) or a table or number line"
That's OK then.

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