y= -2x^2 -5x+3 (1 Viewer)

blacktown_

Member
Joined
Apr 30, 2012
Messages
65
Gender
Male
HSC
2013
so when i use the quadratic formula, i get x = -3 and x= 1/2

but when i use the quadratic factorising method, i get the wrong answers!
can someone help me please?
how do i get the right answer using the quadratic factorising methid ?
 

Aysce

Well-Known Member
Joined
Jun 24, 2011
Messages
2,394
Gender
Male
HSC
2012
y = -2x^2 -5x + 3

So factorising, we should get:

y = (-2x + 1)(x+3)

Let y=0,

x = 1/2 and x=-3
 

blacktown_

Member
Joined
Apr 30, 2012
Messages
65
Gender
Male
HSC
2013
btw, i got this:
0= -2x^2-5x+3
(-2x-3) and (x+1)

therefore x= 1 and x= -2/3

why isn't this right?
 

D94

New Member
Joined
Oct 5, 2011
Messages
4,426
Gender
Male
HSC
N/A
btw, i got this:
0= -2x^2-5x+3
(-2x-3) and (x+1)

therefore x= 1 and x= -2/3

why isn't this right?
If you multiply that out: (-2x-3)(x+1) = -2x2-3x-2x-3 = -2x2-5x-3 ≠ -2x2-5x+3
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top