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Day 2 : Choosing the right Expression to addDescription: Creating an expression to add to another expression
Objective: In previous exercises you were given two expressions to combine together and gave the result, in this exercise you choose an expression that will give the desired outcome when added to other expressions.
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In this exercise you'll be figuring out what expression you need to add on.

The aim in the exercise is to find an expression that when it is :

added to Expression 1 - the answer is only variable

added to Expression 2 - the answer is only constant (no variable part)


Example  What expression do I add to 1)  30 + 4n , 2) 50 - 2n so that the first part is only variable and the second part is only constant.

Answer : you need to add  -30 to make the first part only variable and +2n to make the second part only constant.  So your answer is

  -30 + 2n.

You need to give the result when you add this expression to the other two expressions.

1) 30 + 4n   +  (-30 + 2n)

= 6n

2) 50 -2n  + (-30 + 2n)

= 20

The full answer that you give is then  

-30 + 2n , 6n, 20

Your chosen expression , result when added to the first part,  result when added to the second part.

The three parts to your answer are seperated by commas.


Example question:

Expr1)   12 -5n 

Expr2)     -30 +6n


-12 -6n, -11n, -42


Example question:

Expr1)   -5 + 8n 

Expr2)     30 +6n


+5 -6n, 14n, 35


Example question:

Expr1)   -10 + 5n 

Expr2)     30 - 6n


+10 +6n, 11n, 40


You should notice that every time your expression is just the negative of the constant part (of expression1) and the negative of the variable part (of expression 2).