Distributive property

[KPM]

Hi everyone.

Thank you in advance.

I am struggling with something while using the Khan academy.

When faced with a problem like "choose a like expression for: 3x + 3(x + y)"

Their correct answers are:

1) 6x + 3y
2) 3(x + x + y)

I know I am wrong and this should not be that complicated. However I keep thinking these situations equate to:

3x + 3 (x + y) = 3x ( x + y) + 3 ( x + y) = 3x + 3y + 3x + 3y

I am getting confused as to how to apply the distributive property when there is more than one number/expression outside the parenthesis.

How do you know which one to multiply by?

n.b. I think this is also why I am struggling on nested fractions on there, but will create a separate post as don't want to overload this one.

Thank you for your help

Kpm

 

[Dr.Peterson]

When faced with a problem like "choose a like expression for: 3x + 3(x + y)"

Their correct answers are:

1) 6x + 3y
2) 3(x + x + y)

I know I am wrong and this should not be that complicated. However I keep thinking these situations equate to:

3x + 3 (x + y) = 3x ( x + y) + 3 ( x + y) = 3x + 3y + 3x + 3y

I am getting confused as to how to apply the distributive property when there is more than one number/expression outside the parenthesis.

How do you know which one to multiply by?

n.b. I think this is also why I am struggling on nested fractions on there, but will create a separate post as don't want to overload this one.

Thank you for your help

Kpm

Watch the order of operations!

The expression 3x + 3(x + y) means that (x + y) is multiplied only by 3, not by (3x + 3).

So you must only distribute the 3: 3x + 3(x + y) = 3x + 3x + 3y.

 

[KPM]

Watch the order of operations!

The expression 3x + 3(x + y) means that (x + y) is multiplied only by 3, not by (3x + 3).

So you must only distribute the 3: 3x + 3(x + y) = 3x + 3x + 3y.

Thank you so much Dr Peterson! I had sat there and totally lost sight of the problem, it now seems so obvious ?‍. I can now crack on.

Really appreciate you taking time to reply and help.

Best wishes

Kpm