Can you check my answer and the work? Thank youu~~

(2x-y)7

128x7 -448x6y -672x5y2 -560x4y3 -280x3y4 -84x2y5 -14xy6 -y7

orr

128x7 -448x6y +672x5y2 - 560x4y3 +280x3y4 -84x2y5 +14xy6 -y7

Ps: the 7 in the equation is the exponent and the numbers after the variable are also the exponent

+ 672x^5y^2 - 280x^3y^4 + 14xy^6

only the signs were wrong for the above
corrections

I used an online calculator to expand so I know it's right

so is it this?

128x7 -448x6y +672x5y2 - 560x4y3 +280x3y4 -84x2y5 +14xy6 -y7

or

128x7 -448x6y +672x5y2 -280x3y4 +14xy6

?

sorry, I didn't see your 2nd line after

"or", so the correction applies to your first line/answer

k thank youuu~~~ =)

you're welcome

To verify your answer, we can expand the expression using the binomial expansion formula.

The binomial expansion formula is given as:

(a + b)^n = nC0 * a^n * b^0 + nC1 * a^(n-1) * b^1 + nC2 * a^(n-2) * b^2 + ... + nCn * a^0 * b^n

In this case, the expression is (2x-y)^7.

We can rewrite this as:

(2x - y)^7 = C70 * (2x)^7 * (-y)^0 + C71 * (2x)^6 * (-y)^1 + C72 * (2x)^5 * (-y)^2 + ... + C77 * (2x)^0 * (-y)^7

Where Cnr represents the binomial coefficient, defined as n! / (r! * (n-r)!).

Now, let's simplify it step by step.

C70 * (2x)^7 * (-y)^0 simplifies to:

1 * (2x)^7 * 1 = 128x^7

Next, C71 * (2x)^6 * (-y)^1 simplifies to:

7 * (2x)^6 * (-y) = -448x^6y

Continuing this process for each term, we get the following expression:

128x^7 - 448x^6y + 672x^5y^2 - 560x^4y^3 + 280x^3y^4 - 84x^2y^5 + 14xy^6 - y^7

Comparing this with your answer, it matches the second expression you provided:

128x^7 - 448x^6y + 672x^5y^2 - 560x^4y^3 + 280x^3y^4 - 84x^2y^5 + 14xy^6 - y^7

Therefore, your second answer is correct.