Help with daughters homework (pt 2)

[fatblokish]

Can you please help solve the following:

if a) y=4x^2 and b) z= 8/x

show that z=cy^n where c>0

I've done the following; if this is of any use AND is correct?

a) b)
y/4=x^2 z/8=1/x
sqrt(y/4)=x 8/z=x

combining em gives;
sqrt(y/4) = 8/z

then inverting
sqrt(4/y) = z/8
z=8(sqrt(4/y))
but get stuck here

ta

 

[fatblokish]

damn, formatting went to pot

a)
y/4=x^2
sqrt(y/4)=x

b)
z/8=1/x
8/z=x

combining em gives;
sqrt(y/4) = 8/z

then inverting
sqrt(4/y) = z/8
z=8(sqrt(4/y))
but get stuck here

 

[marinyork]

You need to use surds to sort it out.

 

[Red Light]

damn, formatting went to pot

a)
y/4=x^2
sqrt(y/4)=x

b)
z/8=1/x
8/z=x

combining em gives;
sqrt(y/4) = 8/z

then inverting
sqrt(4/y) = z/8
z=8(sqrt(4/y))
but get stuck here

So z=16sqrt (1/y) = 16y^(-0.5)

Therefore c=16, n= -0.5 in z=cy^n QED

 

[gbb]

Well done for getting that far Fatblokish..
If it'd been my daughter, her book would have been passed straight back over the table......no, sorry pet.

I remember having mumps when i was at school. When i got back, they already started this stuff, i was behind, missed the basics, worse than that, i never got a handle on it at all. Absolute gobbledegook. I'm impressed anyone can do it.

 

[fatblokish]

most excellent, now I can, at your kind expense, continue with my parental aurora intact !

Ta very muchly

 

[marinyork]

I remember having mumps when i was at school. When i got back, they already started this stuff, i was behind, missed the basics, worse than that, i never got a handle on it at all. Absolute gobbledegook. I'm impressed anyone can do it.

One can learn at any age.

√(4a) = √(2²a) = √(2²)√a = 2√a.

It just uses rules of indices and surds. √x.√y = √(xy) and something squared that you apply a square root to, they cancel out.

ICBST 1/ √(4/y). = √(y/4) which is a useful trick. So you get x = ±√(y/4) etc and sub in like that as redlight has done.

You can just use the rules of indices too.

y^(½)y^(-1)= y^(0.5-1) = y^(-½) etc if you want to do it the other way or without the shortcut.

 

[biggs682]

all i got was a headache sorry

 

[threebikesmcginty]

Is the answer Swindon?

 

[Doseone]

This frightens the life out of me. My daughter has recently started high school and I dread the day I can no longer help with her homework. I wouldn't know where to start with this.

 

[ColinJ]

Am I the only one that thinks "It's her homework, why isn't she doing it?" ...

My mum taught me to read before I went to school and from that point on it was up to the schools to teach, me to learn and me to do my homework!

My sister phoned me once to try to get me do her daughter's homework for her but I refused because I couldn't see how that would really help her. What I did do was keep them on the line while I found a really good website that explained the mathematical techniques that she needed to use and then she did it herself. (Actually, I suspect that my sister did it using the techniques described, but what can you do ...?)

 

[Yellow Fang]

It's understanding the question that's the tricky bit. You could do the alegebra and work out z = 16/root(y) but then be puzzled where c and n came in. I think the question is just asking you to show that z is a function of a constant and a power of y.

 

[swee'pea99]

I can generally manage about questions 1-6 of my 12 year old's maths hw...by the time you get to the question 10 I'm lost. As for the 15 year old's, ferget it!

 

[Red Light]

Am I the only one that thinks "It's her homework, why isn't she doing it?" ...

My mum taught me to read before I went to school and from that point on it was up to the schools to teach, me to learn and me to do my homework!

My sister phoned me once to try to get me do her daughter's homework for her but I refused because I couldn't see how that would really help her. What I did do was keep them on the line while I found a really good website that explained the mathematical techniques that she needed to use and then she did it herself. (Actually, I suspect that my sister did it using the techniques described, but what can you do ...?)

I agree generally but there is a difference between tutoring her through her homework and doing it for her. The latter may get her good (or bad!) marks for homework but will get much worse marks when it matters, in exams.

 

[subaqua]

Am I the only one that thinks "It's her homework, why isn't she doing it?" ...

My mum taught me to read before I went to school and from that point on it was up to the schools to teach, me to learn and me to do my homework!

My sister phoned me once to try to get me do her daughter's homework for her but I refused because I couldn't see how that would really help her. What I did do was keep them on the line while I found a really good website that explained the mathematical techniques that she needed to use and then she did it herself. (Actually, I suspect that my sister did it using the techniques described, but what can you do ...?)

wrong, learning is a process that continues at home with the support of parents/adults with parental responsibility ( PC obblocks) . it is not something that should be done only by teachers between 8.30 and 3.30. there are a lot of teachers who understand things one way when there are lots of ways of getting the same result. you may have been able to explain the problem slightly differently to the teacher and your neice may have "got it" I had terrible trouble understanding triangle theorems at preGCSE ( old 3rd year secondary). i asked another maths teacher to explain and got a different explanation that made sense and it was easy after that. I asked my parents with a lot of maths and science but both of them never finished school formally so didn't have a clue. nature ,english, history yes - but sciences no chance.

eldest in in KS2 year and we are helping her with the mental maths in a way that she doesn't realise she is being helped. watching the darts and snooker is fun with this. shiopping is also great for this