Can someone please tell me whether these are correct / how to fix them if they aren't?

(a)



(b)

Close, but you have a couple of mistakes. In the first expression, you got all of the coefficients right, but many of the signs are wrong. If it was , all the coefficients would be positive, of course. Since there's a negative sign in front of the b, however, all the terms with odd powers of b will be negative. Hence it would be .

In the second case, you have the same issue with the signs, plus you also have to make sure you include the 2 when raising 2x to various powers. Hence, it should be , for example.

Quote:

---

Originally Posted by jcaron2

Close, but you have a couple of mistakes. In the first expression, you got all of the coefficients right, but many of the signs are wrong. If it was , all the coefficients would be positive, of course. Since there's a negative sign in front of the b, however, all the terms with odd powers of b will be negative. Hence it would be .

In the second case, you have the same issue with the signs, plus you also have to make sure you include the 2 when raising 2x to various powers. Hence, it should be , for example.

---

Thanks! That was very helpful.

Quote:

---

Originally Posted by Communist

Thanks! That was very helpful.

---

You're welcome!