Answer:
1 + 14x + 84x^2 + 280x^3 or
128x^7 + 448x^6 + 672x^5 + 560x^4.
(see explanation),
Step-by-step explanation:
They are 1^7 + 7C1 1^(7-1)(2x) + 7C2 1^5 (2x)^2 + 7C3 1^4 (2x)^3
= 1 + 14x + 21* 4x^2 + 35*8x^3
= 1 + 14x + 84x^2 + 280x^3
If you require the answer in descending degrees of x by a similar method the answer is:
128x^7 + 448x^6 + 672x^5 + 560x^4.
