ExamSolutions
17th November 2007, 09:39 AM
Take care when writing the square of a negative number.
So often I see students writing things like -3 and quoting the result as 9, it doesn't. If you entered this on a calculator you would get -9.
Why is this? Writing -3 is short for -1 x 3 = -1 x 9 = -9
Always put the negative number to be squared in brackets so that
(-3) = 9.
This error becomes very evident when a square cannot be done mentally such as when there is a horrible decimal such as -3.256 say to square. The answer is not mentally obvious so a calculator is used and then errors more often than not are made.
Enter (-3.256) to get 10.601536
So often I see students writing things like -3 and quoting the result as 9, it doesn't. If you entered this on a calculator you would get -9.
Why is this? Writing -3 is short for -1 x 3 = -1 x 9 = -9
Always put the negative number to be squared in brackets so that
(-3) = 9.
This error becomes very evident when a square cannot be done mentally such as when there is a horrible decimal such as -3.256 say to square. The answer is not mentally obvious so a calculator is used and then errors more often than not are made.
Enter (-3.256) to get 10.601536