Question

Ok now Im stuck lol
What is the X=A OR X=B of
4x^2 - 10x - 9 = 0
I got to:
(x - 5/4)^2 - 136/16
Would it be X=5/4 OR X= -136/16
Could anyone say if this is right or if I am wrong and give the correct X=A OR X=B? Please?

Answer 1

Do you know the quadratic formula?

x= (-b +/- sqrt(b*b -4*a*c))/2a

Answer 2

yh but its a -root which I was told was going the wrong way

Answer 3

Oh I see you did complete the square?

Answer 4

Yh lol That was what the Question asked.

Answer 5

I haven't checked your answer, but shouldn't it be an equation:
(x - 5/4)^2 - 136/16 = 0

Answer 6

If so, move the -136/16 to the right hand side, and then take the square root

Answer 7

I checked your work, and where you got -136/16, it should be -61/16

But assuming you fix your mistake, you would have

(x-5/4)^2 - 61/16=0
or
(x-5/4)^2= 61/16

take the square root of both sides
\[x-\frac{5}{4}= \pm\frac{\sqrt{61}}{4}\]
and
\[x= \frac{5}{4}\pm\frac{\sqrt{61}}{4}\]

Answer 8

Thanks

Answer 9

yw, but I'm still trying to guess how you got 136

Answer 10

That was the problem D: Ill ask about it tommorow in my lesson.

Answer 11

I was doing...
4x^2 - 10x - 9 = 0
4(x^2 - 10x/4 - 9/4)=0
therefore if 4(0)=0
x^2 - 10x/4 - 9/4 = 0
(x - 10/4)^2 - 100/16 - 36/16
(x - 10/4)^2 - 136/16
I got the - 100/16 from removing the remainder from ((10/4)x(10/4)) and the 36/16 from 9/4

Answer 12

oh i see it was (x-5/4)^2??? not (x-10/4)
so that would of gave -25/16 - 36/16 = - 61/16 - ahh thats why i got stuck

Answer 13

Thanks much

Answer 14

OK, you have -10x/4 (btw, I would reduce that to -5x/2 )
so you square half of it: -5/4 * -5/4 = -25/16. You squared the whole thing.

Answer 15

mystery solved!