Need Help With A* GCSE Question ?

[Pearl Drummer]

Hey guys I got my maths mock GCSE paper back and I did pretty well, but I want to know how figure out this insanely hard question?

Find algebraically the coordinates of the points of intersection of the curve y=x² + 7x + 9 and the line y= x + 4 ?

 

[Morba]

6 and 7

 

[Ricochet J]

Solve them simultaneously. Either eliminate x or y, or substitute one equation into the other.

It should give
x=-5 when y=-1 i.e. (-5,-1)
x=-1 when y=-3 i.e. (-1,3)

Edit: I got my factorisation wrong!

 

[Pearl Drummer]

btw the answer box is like this (_,_) (_,_) So a co-ordinate for the line and the curve

 

[Stewy]

Substitution, so you know y= x + 4, so you sub (x+4) in as y so you get
x + 4 = x^2 + 7x + 9. =
x^2 + 6x + 5 =
(x + 5)(x + 1) therefore x = -5 and -1,
then sub back in...
when x = -5, y = -1, and when x = -1, y = 3

So...
(-5, -1)(-1, 3)


I think...

 

[SpaghettiOs]

Substitution, so you know y= x + 4, so you sub (x+4) in as y so you get
x+4 = x^2 + 7x + 9. =
x^2 +6x + 5 =
(x+5)(x+1) therefore x = -5 and -1,
then sub back in...
when x = -5, y = -1, and when x = -1, y = 3.

I think...

Yep. This.

 

[Hxc]

If y=x² + 7x + 9 and y= x + 4
x² + 7x + 9 = x + 4
x² + 6x + 5 = 0
(x + 5)(x + 1) = 0
x = -5 or -1

Sub in those x coordinates
y = -5 + 4
y = -1 + 4
y = -1 when x = -5
y = 3 when x = -1

-5, 1
-1, 3

 

[Stewy]

That brought back some memories

 

[Pearl Drummer]

Thanks Guys, Im getting the jist of it now

 

[Pearl Drummer]

That question was a 5 mark one out of the possible 50 :O

 

[titaniumx3]

I remember a time when that question was considered quite easy.

 

[scrlk]

http://www.wolframalpha.com/ ?

 

[.Andy]

*mutters youth of today, clicks back...*

 

[Jony27]

oh i remember these questions, i feel your pain
currently doing statistics and havent got a clue on standard deviations lol

 

[HAz]

did this for 2 years at college and forgot it all! this was 10 years ago mind. Has it helped me in life? nope not one bit lol.

 

[Dave]

> maths mock GCSE paper

> insanely hard question??

 

[D D Danneh]

I remember a time when that question was considered quite easy.

It still is, so right back at ya

 

[Steve2000]

I couldn't fathom that ****** out if my life depended on it.

 

[Fenris]

It may as well be swahili for how much sense that made to me.

 

[G-MAN2004]

It may as well be swahili for how much sense that made to me.

It's really quite simple once you've done a couple of them.