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# Help with Maths!!! Watch

1. I need help with Maths will be great if someone could explain some questions to me.

3x₂ - 14x - 5
2. Post in the maths help forum
3. 3x^2 - 14x - 5.
This factorises to
(3x +1)(x -5)

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4. (Original post by Tinka99)
I need help with Maths will be great if someone could explain some questions to me.

3x₂ - 14x - 5
The way I like to do it is:

Where you have ax^2 + bx + c, first evaluate ac. In your question, that's 3 x -5 which is equal to -15. Then consider factors of -15 whose summation would equal b (-14). 3 and 5 are factors of 15 but I cannot arrange these in a way to get -14. 15 and 1 are factors too -- you can add +1 to -15 and get -14. Great! So take these new factors and substitute them for the value of b which here is -14 -- we just showed that we can do this because +1 and -15 = -14.

Now we have 3x^2 +1x -15x -5
Now find a factor for the ax^2 and the first x term. x is a factor of both: x(3x+1).

Now repeat the bracket for the next two terms and find what is left to complete the factorisation: x(3x+1)??(3x+1).
What is left is clearly -5 so we can write x(3x+1)-5(3x+1) which is the same as saying (x-5)(3x+1)

When f(x) = 0, x = 5 or x = -1/3.
we could also call this y but since that wasn't stipulated the more general case of 'where in this function of x, x is zero' is better.

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