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# Tough maths question- Can anybody answer this? watch

1. (Original post by Mathsgu)
The question is:

Change one value in the equation so that there is one solution

2xsquared + 7x + 3 =0

Give as many possible solutions as you can.
You mean find x or change either 2,7,3?
If it's x then the answers are -3 & -1/2

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2. 2 change to 49/12 or
7 change to +- root 24 or
3 change to 49/8
3. (Original post by Mathsgu)
The question is:

Change one value in the equation so that there is one solution

2xsquared + 7x + 3 =0

Give as many possible solutions as you can.
Do you know how to check whether a quadratic equation has a repeated root and so one one solution?
4. Basically change any value within the equation, either the x or the 7 or the 3 values. And by changing this equation will only give one x value when solved, no the two solutions that this equation has at the moment.

Hopefully that will make sense. Here's a picture of the question if that helps.
Attached Images

5. (Original post by ian.slater)
Do you know how to check whether a quadratic equation has a repeated root and so one one solution?
No I'm not sure on how to do that although I can vaguely remember covering it
6. (Original post by Mathsgu)
No I'm not sure on how to do that although I can vaguely remember covering it
The solutions to the equation ax^2 + bx + c = 0 are given by the well-known formula:

x = (-b+/-sqrt(b^2-4ac)/2a

so you normally get two solutions. But if the bit in the sqrt is zero, you only get one.

That bit, b^2 - 4ac , is called the discriminant.

So what do you have to change the coefficients to, in order to make the discriminant zero? You can change one of a, b or c at a time.
7. (Original post by Kim-Jong-Illest)
2 change to 49/12 or
7 change to +- root 24 or
3 change to 49/8
8. (Original post by ian.slater)
The solutions to the equation ax^2 + bx + c = 0 are given by the well-known formula:

x = (-b+/-sqrt(b^2-4ac)/2a

so you normally get two solutions. But if the bit in the sqrt is zero, you only get one.

That bit, b^2 - 4ac , is called the discriminant.

So what do you have to change the coefficients to, in order to make the discriminant zero? You can change one of a, b or c at a time.
Exactly
One "delta" (how I call that formula) that gives zero is 4^2-4.1.4 so b=4 a=1 c=4

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9. (Original post by ian.slater)
The solutions to the equation ax^2 + bx + c = 0 are given by the well-known formula:

x = (-b+/-sqrt(b^2-4ac)/2a

so you normally get two solutions. But if the bit in the sqrt is zero, you only get one.

That bit, b^2 - 4ac , is called the discriminant.

So what do you have to change the coefficients to, in order to make the discriminant zero? You can change one of a, b or c at a time.
Thanks for the help I can remember doing something like that.
10. (Original post by Mathsgu)
I think I worked out how to do it now
11. (Original post by Mathsgu)
The question is:

Change one value in the equation so that there is one solution

2xsquared + 7x + 3 =0

Give as many possible solutions as you can.
you just need to make b^2 - 4ac = 0, and you will have one solution.
12. (Original post by rock_climber86)
you just need to make b^2 - 2ac = 0, and you will have one solution.
Thanks, I didn't realise how easy it was!
13. (Original post by Mathsgu)
Thanks, I didn't realise how easy it was!
no worries. Interesting question btw. Never seen one like that before!
14. (Original post by rock_climber86)
you just need to make b^2 - 2ac = 0, and you will have one solution.
Watch out it's b^2-4ac=0

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15. (Original post by Pungolini)
Watch out it's b^2-4ac=0

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Thanks for the correction! Innocent typo
16. b^2-4ac=0
Plug in two different values at a time and solve for the remaining variable.
eg. 7^2-4*2*c = 0 so c = 49/8
Repeat for b and a.

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