I'm just learning algebra.
The order of operation rule i learned pre-algebra is: PEMDAS. And you do multiplication and division from left to right as they occur. I also learned that with fractions you solve the numerator first, then you solve the denominator, then you divide. Thats all correct, right?
In my algebra text book it said that in algebra you always write a division sign as a fraction. "Okay, fair enough, i'll obey that rule too" i said.
But then i get a question like this:
9xy / 3x * 2y^2 * 4x^3
So the order of operation states that i do 9xy / 3x first and THEN multiply the rest of the terms to get the answer. Which gives the CORRECT answer.
But the book, as i mentioned earlier, told me the rule with algebra is to write division as a fraction. So if you do that you end up in effect doing this: 9xy / (3x * 2y^2 * 4x^3) because you simplify the numerator and then you simplify the denominator and then you divide numerator by denominator.
So what the ****? Why would the book tell you this rule when it is sometimes wrong and will lead you to get the wrong answer. Am i missing something here? Or was the book right and i have just misunderstood something? Or am i right? Should you look at the question and obey the PEMDAS rule above all else before changing division signs into fractions in algebra questions?
The order of operation rule i learned pre-algebra is: PEMDAS. And you do multiplication and division from left to right as they occur. I also learned that with fractions you solve the numerator first, then you solve the denominator, then you divide. Thats all correct, right?
In my algebra text book it said that in algebra you always write a division sign as a fraction. "Okay, fair enough, i'll obey that rule too" i said.
But then i get a question like this:
9xy / 3x * 2y^2 * 4x^3
So the order of operation states that i do 9xy / 3x first and THEN multiply the rest of the terms to get the answer. Which gives the CORRECT answer.
But the book, as i mentioned earlier, told me the rule with algebra is to write division as a fraction. So if you do that you end up in effect doing this: 9xy / (3x * 2y^2 * 4x^3) because you simplify the numerator and then you simplify the denominator and then you divide numerator by denominator.
So what the ****? Why would the book tell you this rule when it is sometimes wrong and will lead you to get the wrong answer. Am i missing something here? Or was the book right and i have just misunderstood something? Or am i right? Should you look at the question and obey the PEMDAS rule above all else before changing division signs into fractions in algebra questions?