Question

(7k+2)^2-(7k-2)^2 делится на 21 ?

Answer 1

Ответ:

Пошаговое объяснение:

((7к+2-7к+2)(7к+2+7к-2))/21=(4*14к)/21

Нет не делиться 56 не кратно 21

Answer 2

Let's simplify the expression first and then check whether it is divisible by 21.

We have:

(7k + 2)^2 - (7k - 2)^2

Using the identity a^2 - b^2 = (a + b)(a - b), we can rewrite the expression as:

[(7k + 2) + (7k - 2)][(7k + 2) - (7k - 2)]

Now, simplify the expression further:

[(7k + 7k)][(4)]

Now, combine like terms:

[14k][4] = 56k

Now we have the simplified expression: 56k.

To check if 56k is divisible by 21, we need to see if it's divisible by both 7 and 3 (since 21 = 7 * 3).

1. Divisibility by 7: 56k is divisible by 7 because 56 is divisible by 7.

2. Divisibility by 3: To check if k is divisible by 3, we would need more information about the value of k. As it stands, we cannot determine if k is divisible by 3 from the given expression.

Therefore, we cannot definitively say whether the expression (7k + 2)^2 - (7k - 2)^2 is divisible by 21 without more information about the value of k.