Help with math (done)

[-TesseracT-]

Five questions. Ok this might be easy.

1. p(bx + a) = q(x - c)

How can I solve x?------------------------------

2. Four cubes has the combined volume of 13 dm^3. The cubes' sides relates to each other as 2 : 3 : 4 : 5.

What is the length of the smallest cube's side?---------------------------

3. Person A paints a wall in 4 hours. For person B it takes 6 hours to paint the same wall. How long would it take them to paint the wall if they do it together?-------------------------------

4.(x + 2)^2 = 16. How am I supposed to calculate this? I got to x^2 + 4x = 12, then what?-----------------------

5. A balloon rises with a constant velocity h meters in t hours. How high does it rise in n hours?----------------

Ok so that's it

[ind3x]

Question 4 is a quadratic equation and you can find x with this:

 

x^2 + 4x = 12

=>

x^2 + 4x -12 = 0

 

x^2 =a

4x=b

12=x

 

[Archangel1994]

2.

 

To solve it you need to find out what the volume is of the smallest cube which is 2/(2+3+4+5). Then you have the volume of the smallest cube. Then just (I don't know what to call it) take the cube root (Not square root, so the cube root of 8 is 2 because 2^3 = 8) and you have the smallest side.

 

3.

 

Person A does 25% per hour or 0.25X

Person B does 16.67% per hour or 0.1667X

Total is 0.25X + 0.1667X = 1 for the entire wall

 

5.

 

The balloon rises h metres in t hours so it rizes h / t metres per hour (so if it rises 50 meters in 0.5 hours then it will rize 50/0.5 = 100 meters per hour). So in n hours it rizes (h / t) * n

[jurian123]

2.

 

To solve it you need to find out what the volume is of the smallest cube which is 2/(2+3+4+5). Then you have the volume of the smallest cube. The just (I don't know what to call it) take the cube root (Not square root, so the cube root of 8 is 2 because 2^3 = 8) and you have the smallest side.

 

3.

 

Person A does 25% per hour or 0.25X

Person B does 16.67% per hour or 0.1667X

Total is 0.25X + 0.1667X = 1 for the entire wall

 

5.

 

The balloon rises h metres in t hours so it rizes h / t metres per hour. So in n hours it rizes (h / t) * n

Doe jij VWO ofso? (dutch) 

[Archangel1994]

Doe jij VWO ofso? (dutch) 

I'm doing university right now, I have done VWO yes . Besides none of these are very difficult aside from the first one, that one is a bit tricky

[jurian123]

I'm doing university right now, I have done VWO yes . Besides none of these are very difficult aside from the first one, that one is a bit tricky

That is why your are so smart!  

 

I do MBO lvl 4, one lvl lower than HBO! 

[-TesseracT-]

Question 4 is a quadratic equation and you can find x with this:

 

x^2 + 4x = 12

=>

x^2 + 4x -12 = 0

 

x^2 =a

4x=b

12=x

 

lol that's crazy, I have no idea how they thought you could calculate that. Thanks anyways

[Archangel1994]

Done the first one too now. Give me a moment

 

1.

 

p(bx+a) = q(x-c)

pbx + pa = qx - qc

pbx = qx - qc - pa

pbx - qx = -qc - pa

x(pb - q) = -qc - pa

x = (-qc - pa)/(pb - q)

 

Call me out on a mistake I may have made, be it calculation or typing errors

[-TesseracT-]

2.

 

To solve it you need to find out what the volume is of the smallest cube which is 2/(2+3+4+5). Then you have the volume of the smallest cube. The just (I don't know what to call it) take the cube root (Not square root, so the cube root of 8 is 2 because 2^3 = 8) and you have the smallest side.

 

3.

 

Person A does 25% per hour or 0.25X

Person B does 16.67% per hour or 0.1667X

Total is 0.25X + 0.1667X = 1 for the entire wall

 

5.

 

The balloon rises h metres in t hours so it rizes h / t metres per hour (so if it rises 50 meters in 0.5 hours then it will rize 50/0.5 = 100 meters per hour). So in n hours it rizes (h / t) * n

very nice, thank you

[-TesseracT-]

Done the first one too now. Give me a moment

 

1.

 

p(bx+a) = q(x-c)

pbx + pa = qx - qc

pbx = qx -qc - pa

pbx - qx = -qc - pa

x(pb - q) = -qc - pa

x = (-qc - pa)/(pb - q)

 

Call me out on a mistake I may have made, be it calculation or typing errors

It says in the book:

 

x = (ap + cq)/(q - bp).

 

The original thing was (bx + a)/q + (x - c)/p

So I multiplied both numerators with qp, was left with p(bx+a) = q(x-c) . Should I have done that?

[Guest]

UGH

 

math

[-TesseracT-]

Lol I just want a damn C on my test tomorrow lol

[Archangel1994]

It says in the book:

 

x = (ap + cq)/(q - bp).

 

The original thing was (bx + a)/q + (x - c)/p

So I multiplied both numerators with qp, was left with p(bx+a) = q(x-c) . Should I have done that?

You made a mistake there. The original is (bx+a)/q + (x-c)/p. That means if you bring the (x-c)/p to the right of the equals sign it becomes MINUS (x-c)/p. Not plus

[VMaxMuffin]

 

Done the first one too now. Give me a moment

 

1.

 

p(bx+a) = q(x-c)

pbx + pa = qx - qc

pbx = qx - qc - pa

pbx - qx = -qc - pa

x(pb - q) = -qc - pa

x = (-qc - pa)/(pb - q)

 

Call me out on a mistake I may have made, be it calculation or typing errors

 

 

It says in the book:

 

x = (ap + cq)/(q - bp).

 

The original thing was (bx + a)/q + (x - c)/p

So I multiplied both numerators with qp, was left with p(bx+a) = q(x-c) . Should I have done that?

 

@Archangel1994 has the same answer as the book just expressed slighty differently

 

ap = pa

cq = qc

bp = pb

 

so:

(-qc-pa)/(pb-q) = (-cq-ap)/(bp-q) = [-(ap+cq)]/[-(q-bp)] = (ap+cq)/(q-bp) {negatives cancel in this last step}

[VMaxMuffin]

And I think all the questions have been solved but tag me if you need alternative solutions or explanations because I'll be able to help

[Archangel1994]

And I think all the questions have been solved but tag me if you need alternative solutions or explanations because I'll be able to help

I knew I forgot something. Thanks for the negative cancellation

[-TesseracT-]

You made a mistake there. The original is (bx+a)/q + (x-c)/p. That means if you bring the (x-c)/p to the right of the equals sign it becomes MINUS (x-c)/p. Not plus

omg sorry. The original thing was (bx + a)/q = (x - c)/p

 

So to get rid of /q and /p you must multiply both sides with qp right

[-TesseracT-]

@Archangel1994 has the same answer as the book just expressed slighty differently

 

ap = pa

cq = qc

bp = pb

 

so:

(-qc-pa)/(pb-q) = (-cq-ap)/(bp-q) = [-(ap+cq)]/[-(q-bp)] = (ap+cq)/(q-bp) {negatives cancel in this last step}

yes ofc

[Archangel1994]

omg sorry. The original thing was (bx + a)/q = (x - c)/p

 

So to get rid of /q and /p you must multiply both sides with qp right

Aaaaah do it right immediately . I got all confused about my calculations now. Yes you need to multiply both sides by pq.

[GarnetDevil]

I'll make the math equation equation easier for you

 

1. x= (-ap-qc)/(pb-q)

 

4. (x+2)^2=16 => x+2=4 OR x+2=-4

[Archangel1994]

What you can also do is because both the left and right term are fractions   like this you can also do something else.

 

Say you have 2 fractions   and  . You can do cross multiplication with this. Take the top of the left fraction and multiply it with the bottom of the right fraction and vice versa. This will give you 3*4 = 3*4 in this example.

[-TesseracT-]

How can (1/5)^-2 be 25?

 

2 / (1/5) = 2 * (5/1) = 10/1 ???

[Nineshadow]

How can (1/5)^-2 be 25?

 

2 / (1/5) = 2 * (5/1) = 10/1 ???

(1/5)^-2 = 5² = 25

 

a^-n = (1/a)ⁿ

[GarnetDevil]

How can (1/5)^-2 be 25?

 

2 / (1/5) = 2 * (5/1) = 10/1 ???

(1/5)^-2 means (1/1/5)^2 or 5^2 = 25

[Archangel1994]

How can (1/5)^-2 be 25?

 

2 / (1/5) = 2 * (5/1) = 10/1 ???

1/5 = 0.2

0.2 ^-2 = 25

 

Remember that is exponent, not just multiplication