# maths questions I don't understandWatch

Thread starter 4 years ago
#1
Can someone please explain these solutions please? I'm so confused!

1. 6x2-22x-8

I got the answer as (6x+2)(x-4) but the answer is actually 2(3x+1)(x-4)
why do I need to take the 2 out when I can factorise it already?

2. -4x2+7

I worked it out as (2x-)(2x+ but the solution says -(2x-)(2x+. I already multiplied by -1 at the start to get rid of -4x so why do I have to multiply by -1 again?
0
4 years ago
#2
(Original post by HelloGoodbye)
Can someone please explain these solutions please? I'm so confused!

1. 6x2-22x-8

I got the answer as (6x+2)(x-4) but the answer is actually 2(3x+1)(x-4)
why do I need to take the 2 out when I can factorise it already?

2. -x4x2+7

I worked it out as (2x-)(2x+ but the solution says -(2x-)(2x+. I already multiplied by -1 at the start to get rid of -4x so why do I have to multiply by -1 again?
(6x+2)(x-4) is factorised but not fully factorised. Since 6x+2 = 2(3x+1) you can factorise further. If a question tells you to factorise, it wants you to factorise fully.

2. If you multiply by -1, it changes the expression i.e. is different to and if you factorise both you will get different answers,

You're probably getting confused with equations where you can multiply by a constant and get away with it e.g. is the same as
1
4 years ago
#3
(Original post by HelloGoodbye)
Can someone please explain these solutions please? I'm so confused!

1. 6x2-22x-8

I got the answer as (6x+2)(x-4) but the answer is actually 2(3x+1)(x-4)
why do I need to take the 2 out when I can factorise it already?

2. -4x2+7

I worked it out as (2x-)(2x+ but the solution says -(2x-)(2x+. I already multiplied by -1 at the start to get rid of -4x so why do I have to multiply by -1 again?
Hiya,
For the first question, you have got the correct answer but they've fully factorised it by pulling out another factor of 6 & 4 which is 2.

For the 2nd question you need to multiply it by -1 to get the -4xÂ². In your answer you have 2x X 2x which is 4xÂ² not -4xÂ² so it must be x by -1 to make it correct. Also I think for the âˆš that -âˆš7 x +âˆš7 = -7 so you have to x by -1 to get 7(I'm not sure)
0
X

new posts
Back
to top
Latest
My Feed

### Oops, nobody has postedin the last few hours.

Why not re-start the conversation?

see more

### See more of what you like onThe Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

### University open days

• Regent's University London
Thu, 19 Sep '19
• Durham University
Pre-Application Open Days Undergraduate
Fri, 20 Sep '19
• Loughborough University
Fri, 20 Sep '19

### Poll

Join the discussion

Rock (169)
24.56%
Pop (170)
24.71%
Jazz (27)
3.92%
Classical (41)
5.96%
Hip-Hop (125)
18.17%
Electronic (45)
6.54%
Indie (111)
16.13%