It's actually useless for maths as you can't rely on anything it says.
When does BIDMAS fail?
BIDMAS is an acronym used to remember the order of operations in arithmetic and algebra. It stands for Brackets, Indices, Division, Multiplication, Addition, and Subtraction, and tells us the order in which we should perform arithmetic operations in an expression.
BIDMAS is a useful tool for evaluating arithmetic expressions, but it does not apply universally to all mathematical expressions. In particular, BIDMAS fails to account for certain mathematical operations that have no clear precedence.
For example, consider the expression:
1/2x
According to BIDMAS, we should perform division before multiplication, so we might be tempted to evaluate this expression as:
1/2 * x = 0.5x
However, this is not correct. The correct way to evaluate this expression is to recognize that the division symbol does not only apply to the 1 and the 2, but also to the variable x, which is effectively being divided by 2. So the correct answer is:
1/2x = (1/2)*x = 0.5x
Another example of where BIDMAS fails is with regards to exponents and roots. In some cases, it may not be clear whether an exponent or a root should be evaluated first. For example, consider the expression:
-4^(2/3)
Using BIDMAS, we might be tempted to evaluate the exponent before the negative sign, resulting in:
-4^(2/3) = -2.51984
However, this is not the correct answer. The negative sign applies to the entire expression, so we need to evaluate the root before applying the negative sign, resulting in:
-4^(2/3) = -(4^(2/3)) = -2.51984i
In summary, BIDMAS is a useful tool for evaluating arithmetic expressions, but it is not a universal rule that applies to all mathematical expressions. It can fail to account for certain operations that have no clear precedence, such as division and multiplication, or exponents and roots, so it is important to use good judgment and understanding of the mathematical rules when evaluating more complex expressions.