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Algebra 1 homework problem?
I'm helping a girl in my class who got sick and fell behind catch back up, and my teacher told me to go back over the review sheet so I make sure I remember everything from the last lesson. I'm having a little trouble with a few problems.. I have the answers so that's not what I need. What I need is an explanation of how to get that answer. So here it goes..
Evaluate f(x)= -x^2 + 1 for x= -3. The answer is -8. I got 10. I understand what I did wrong, but can you explain why I shouldn't drop the negative sign when I plug in -3 for -x?
Graph the function. Use x = -2, -1, 0, 1, and 2 for the domain
y= |x| - 1. I just flat out don't understand absolute values. Please explain how to work problems like this. I get the graphing part so no need to explain that.
y = |x| + 3. Same instructions as the last problem. Again, I suck at absolute value problems..
thanks so much for the help!
2 Answers
- anonymousPersonLv 78 years agoFavorite Answer
If you plug -3 into (-x)^2 + 1, that would be (- -3)^2 + 1 = 3^2 + 1 = 10. Unless there are parentheses, though, you should apply the exponent and then the negative sign, so it would be -(3^2) + 1 = -9 + 1 = -8.
Absolute values just make whatever is in them positive. If you have |-2|, that would be 2. If you have |2|, that would also be 2. If you have |-2| - 1, apply the absolute value and subtract; that's 2 - 1 = 1. |-1| - 1 = 1 - 1 = 0. |0| is just 0, so |0| - 1 = -1. 1 and 2 are already positive, so applying the absolute value doesn't change anything; |1| - 1 = 1 - 1 = 0, and |2| - 1 = 2 - 1 = 1.
Same thing for the last one. |-2| + 3 = 2 + 3 = 5. And so on.
Source(s): http://www.math-prof.com/ -- Check out the pre-algebra section. - ?Lv 78 years ago
Evaluate f(x)= -x^2 + 1 for x= -3. The answer is -8. I got 10. I understand what I did wrong, but can you explain why I shouldn't drop the negative sign when I plug in -3 for -x?
There is a difference between -x^2 and (-x)^2. The first one is the negative answer of x^2. The second one is the square of negative x.
Example x = (-5)
-x^2 is the negative answer of (-5)^2
(-5)^2 =25
but
-(-5)^2 = - 25
Example x = (-5)
(-x^2) is
(- (-5)^2 the negative of a negative is a positive so it's really 5^2 = 25
