Question

Write down the first 4 terms in the expansion of (1+2x)^7 ​

Answer 1

1 + 14x + 84x^2 + 280x^3 or

128x^7 + 448x^6 + 672x^5 + 560x^4.

(see explanation),

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.

Answer 2

If you don’t know the answer, just type “Love”
If the teacher said it’s wrong.. ask him,

“What is wrong with love?”