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Hence solve the equation - OCR Maths

Solve the equation y²-7y+12=0

Hence solve the equation x4-7x²+12=0

I understand how to factorise the first part but how do i use that to help with the second equation.
Reply 1
Avatar for Amber20
Amber20
1
so the first part factorised is (y-3)(y-4)
the second equation is pretty much the same it just has different powers of x
so you take the first answer switch the y's for x's and make it x squared because x^2 times x^2 is x^4
Reply 2
Avatar for JN17
JN17
10
The second equation has just used the substitution of y = x^2, so in your answer to part a), do the same and replace y with x^2 and solve this.
Reply 3
Avatar for pbms0101
pbms0101
OP
Thank you but why do you use x^2?
Original post by pbms0101
Thank you but why do you use x^2?


Well, what happens when you put y = x^2 into the new equation you have been asked to solve?

Also, if you quote someone like I have done so now, they will know you have responded :smile:
(edited 7 years ago)
Original post by pbms0101
Thank you but why do you use x^2?


You have x4−7x2+12=0x^4-7x^2+12=0

We can make it look like a quadratic by saying: (x2)2−7(x2)+12=0(x^2)^2-7(x^2)+12=0

Now let y=x2y=x^2 and you get y2−7y+12=0y^2-7y+12=0

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