The tutor points out a common error in evaluating expressions.

Most students, from grade 7 on, are familiar with the order of operations BEDMAS (first brackets, then exponents, then division, next multiplication, then addition, finally subtraction). However, sometimes the order gets mistaken.

Example 1: Simplify -(-2)^4

Solution:

The correct way to proceed is to evaluate the exponent (-2)^4 first, which gives 16. Next, multiply it by the negative in the lead, arriving at -16. The correct answer is -16.

The mistake often made is “cancelling” the two negatives by mulitplying them together first. That can’t be done, since it means multiplying before evaluating the exponent.

Example 2: Simplify 2(3)^2

Solution:

The correct way to proceed is to evaluate the exponent (3)^2 first, which gives 9. Next, multiply it by the 2 in front, arriving at 18. The correct answer is 18.

The mistake often made is to multiply before evaluating the exponent, as follows:

2(3)^2=6^2=36 (wrong)

While this mistake might seem obvious, it leads to many lost marks. Sometimes a flaw only becomes obvious after someone points it out (likely because someone pointed it out to them earlier).

HTH:)

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.