Is the text book wrong, or am I just too old for this?...

[arizwldcat]

I haven't used my math in a lot of years...since before the earth cooled, according to my kids. Anyway, I have been helping my daughter with her math homework, and we've been checking the answers provided in the back of the book to see if we're right. For the following problem:

1-3y+y=5

The text book says the answer is -2

I don't understand how that could be. If you add the ys, you have

1-4y=5

(I thought the answer was -1)

Inserting a -2 in the problem, you get

1- (-8)=5

That does not compute.

Or am I just doing it wrong?

:?:

 

[TchrWill]

Re: Is the text book wrong, or am I just too old for this?..

For the following problem:

1-3y+y=5

The text book says the answer is -2

I don't understand how that could be. If you add the ys, you have

1-4y=5

(I thought the answer was -1)

Inserting a -2 in the problem, you get

1- (-8)=5

That does not compute.

Or am I just doing it wrong?

-----------------------------------------------------------
Given 1-3y+y=5

Adding the y's yields -3y + y = -2y not -4y.

1 - 2y = 5 or 2y = -4 making y = -2

 

[stapel]

Re: Is the text book wrong, or am I just too old for this?..

For the following problem:

1-3y+y=5

The text book says the answer is -2

I don't understand how that could be....

The book is correct. For your own purposes, you might want to review how to work with negative numbers. :idea:

Meanwhile: What steps your daughter try? What answer did she get? Please be complete. Thank you!

Eliz.

 

[arizwldcat]

Thanks for your help. I am still confused, however, because I thought the 2y was positive and the - was the operation between the whole number 1 and the 2y. So, you're saying that the 2y is negative? Hmmmm

 

[arizwldcat]

Sorry, I didn't answer your other questions. My daughter and I worked on the problem together, so that I am not sure "she" and "I" got separate answers. Didn't mean to sound incomplete.

 

[Loren]

1-3y+y=5

The text book says the answer is -2

I don't understand how that could be. If you add the ys, you have

1-4y=5

The symbolism can be confusing at times. For it to be according to your interpretation, it would be 1-(3y+y)=5.

I encourage you and your daughter to look up the "order of operations convention." It is very important that it be mastered.
Another suggestion is that you remember that a variable with no preceeding numerical coefficient is understood to have a numerical coefficient of 1. Therefore -3y+1y would be more easily recognized as "subtract 3y, then add 1y leaving you with a negative 2y.
Hope this helps.

 

[stapel]

I am still confused, however, because....

You still need to study how to work with negative numbers. :idea:

Once you learn how integer arithmetic words, you will understand how "subtract three y's and add one y" gives a net "subtract two y's" rather than, as you had thought, "subtract four y's". :wink:

Eliz.

 

[Denis]

Re: Is the text book wrong, or am I just too old for this?..

1-3y+y=5

4 apples - 3 apples = 1 apple ; agree?

1 apple - 3 apples = -2 apples ; see it? Same as yours: one y - 3 y's