If x = -1 and Y = 2, what is the value of the expression 2x3 - 3xy?

Question

could you please break it down for me and I didnt know how to put the 3 over the x

Answer 1

I appreciate your attempt to be clear, in your extra remark. I think you mean 2 (x-cubed) - 3 xy?

Most people using computers write "x-cubed" as: x^3. This is a nice visual way of indicating a "power" following the variable to be cubed. The "^" symbol is present above the "6" on the usual keyboard. It's known technically as the "carat" (NOT "carot") or "hat" symbol (the latter more common among techies). "Hat" is suggestive because it looks like a little hat. You can also think of it as part of a little arrow meaning "put something up there!"

If the power is something more complicated than a single symbol, there's also a convention that the "power" expression has parentheses about it; thus: x^(1/2) and x^(-t). That is also a courtesy to other readers. Many question setters on Yahoo! Answers seem quite unaware of the conventions that aid clarity. This causes an incredible amount of confusion. It's like driving on the highway, paying no attention to the rules of the road, including which side of it should be used! Such question setters seem to expect their readers to be clairvoyant.

Enough of that sermon.

If x = -1 and y = 2, the value of the expression

2 x^3 - 3 x y = 2(-1)^3 - 3(-1)2 = - 2 + 6 = 4.

Live long and prosper.

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POSTSCRIPT

You can actually see the confusion that is possible by not following the usual conventions, in the answers below. It probably stems from not reading your explanatory remark. That shows why it's important to use clear conventions in the main expression of a math-based question.

Another far too common problem is the failure to use brackets to avoid misunderstanding. I appeal to anyone contemplating posing a question to:

GROUP YOUR TERMS PROPERLY!

Answer 2

The answer is 0

2 (-1) - 3(-1) 2
-2( 3 ) - (-3)2
-6 minus -6 = 0

The negative 6's cancel each other out. XY = the amount you have to multiply by. Anytime there is a 2x3 - the x is always mulitplied unless seperated by a different symbol

Answer 3

plug in -1 for x and 2 for y, so,

2x^3 - 3xy
=2(-1)^3 - 3(-1)(2)
=-2+6
=4

p.s. the ^ is found above the 6 on the keyboard and is universal for indicating an exponent

Answer 4

You would do the following:
2(-1)^3-3(-1*2)
2(-1)+6
-2+6
4

Answer 5

2x³ - 3xy = 2(-1)³ - 3(-1)(2) =
2(-1) - 3(-1)(2) = -2 + 6 = 4
Answer is 4.

Attention!
To put the 3 over the x, press ctrl+alt+3, in the same time.
<>>

Answer 6

I am assuming that you mean 2*x cubed - 3*x*y if this is the case then the answer is done like this.

2*(-1)*(-1)*(-1) - 3*(-1)*(2)

so you have

-2 + 6

so the answer is:

4

Answer 7

when x is raised to some number, its written as:
2x^3 - 3xy

First step: the problem gives us the numbers for "x" and "y."

Second step: replace "x" with -1 and replace "y" with 2 in the problem.

2(-1)^3 - 3(-1)(2)

Third step: solve (-1)^3 by breaking it apart
(-1)(-1)(-1) and multiply the first two numbers

which is (1) because when multiplying two negatives, the sign becomes positive. next multiply 1 by the remaining number (-1). (1)(-1) = -1

Fourth step: multiply 2(-1) - 3(-1)(-2)

= -2 - 3(2)
= -2 - 6
= -8

Answer 8

2 times 3 minus 3xy = correct? Well here is my answer.Oh and its better if you write out the problems in words so we can understand exactly what your trying to say.
2 x 3 - 3(-1)(2) = -36

Answer 9

I'm guessing 2x3 is 2x(to the third)


2(-1) to the third - 3(-1)(2)
(2)(-1)+6
-2+6=4

if 3 isn't to the third and its just times 3, then

(2)(-1)(3)-(3)(-1)(2)
-6+6=0

Answer 10

2(x)^3-3xy
2(-1)^3-3(-1)(2) >>-1 cubed is -1 and -3 x -1 is 3 then x 2 is 6

2(-1)+6 -- 2 x -1 is -2
-2+6 = 4

just remember your properties and break it down