Expert: Paul Klarreich - 3/2/2007

Question
Can you check these answer for me..

y=5x^2-10x+7

X                Y=5X^2-10X+7
--------------------------------
-5              Y= 5(-5)-10(-5)+7= 182
-4              Y= 5(-4)-10(-4)+7=127
-3              Y= 5(-3)-10(-3)+7=82 AND SO ON.....
-2
-1
0
1
2
3
4
5

MY DEADLINE NEARS.


Answer
Hi, Pearl,

In your material:

Question:  Can you check these answer for me..

y=5x^2-10x+7

X                Y=5X^2-10X+7
--------------------------------
-5              Y= 5(-5)-10(-5)+7= 182
-4              Y= 5(-4)-10(-4)+7=127
-3              Y= 5(-3)-10(-3)+7=82 AND SO ON.....
-2
-1
0
1
2
3
4
5

The numerical answers appear to be ok, but you are not writing the correct expressions.  Line 1 should say:

-5              Y= 5(-5)^2-10(-5)+7= 182

[i.e. you left out the 'square' symbol, although you seem to have done the squaring, since 182 is correct.

Suggestion: Excel and other spreadsheets are great for this kind of thing.  Write:

Put -5 in a cell, A1, perhaps.
Then put the expression:  =5*A1^2 - 10*A1 + 7 in the adjacent cell.

Put A1+1 in the cell below, A2.
Now do copying and the program automatically adjusts for the locations.

My spreadsheet gives:

-5   182
-4   127
-3   82
-2   47
-1   22
0   7
1   2
2   7
3   22
4   47
5   82