A friend of mine has a question in elementary algebra; none of our friends believe the answer that the test gave, and there is no one around to straighten us out.
Question: If x is equal to negative one, and y is equal to two, can the following equation equal 4?
2x3-3xy?
thanks,
hh
The order of operations says to do exponents first, so 2x[sup]3[/sup] is 2*(-1)[sup]3[/sup]. -1[/sup]3[/sup] is -1, multiplied by two is -2.
3 times -1 is -3, times 2 = -6.
-2 - -6 is the same as -2 + 6 which equals 4.
Wthanks, friedo, but I think that the 3 is not an exponent.
(I was thinking that the problem is a mispring, and that htere is no way ion earth that any math teacher would make 2x3 mean anything other than 2 times 3.)
Is there any other way that this can work?
misprint, of course, not mispring.
(and thanks, not wthanks!)
hh
Hmm, if the 3 is not an exponent, then it works out to -6 + 6 = 0.
I’m a thankin’ ye, friedo!
hh
Is that
2 times 3 = 3 times X times Y
then? The use of ‘x’ as a variable and also as an operand is a bit confusing.
If the question appears exactly as it does in the OP, I’m betting on a misprint. 2x3 would be a totally nonstandard way of writing “2 times x times 3,” nor would “x” be used to indicate multiplication in the same context in which the letter x is being used as a variable.
Plus, it’s not an “equation”: there’s no = sign.
I’ll chime in that an equation cannot equal anything. An expression can equal something. An equation can be solved for a variable, or can be valid/invalid, but it cannot ‘equal’ anything in conventional algebra.
Indeed. There’s also the inconsistency of writing “2x3” to mean 2 * 3 and then “3xy” to mean 3 * x * y.
Since (as friedo so cogently notes) treating the first 3 as an exponent gives the expected result, it’s tempting to think that this is what was intended.