Question

If x + 5 is a multiple of 3, which of the following MUST be a multiple of 9?
A. X^2+ 25
B. 3x + 5
C. (x + 5)(x + 5)
D. (x + 5)(x +9)
please help me to solve this.
please...​

Answer 1

Answer:

C (X + 5)(X + 5)

Step-by-step explanation:

Given

( X + 5) = 3m [ Multiple of 3]

squaring Both Sides

(X + 5)(X + 5) = 3m * 3m

(X + 5)(X + 5) = 9 m²

so Option C

Answer 2

Answer:

(x + 5)(x + 5)

Step-by-step explanation:

As x + 5 is a multiple og 3, let that be 3n. Means,

Let, x + 5 = 3n.

So, square on both sides,

=> (x + 5)² = (3n)²

=> (x + 5)(x + 5) = 9n²

As RHS contains 9, (x + 5)(x + 5) is a multiple of 9.

Other numbers may or may not be a multiple of 9, but (x + 5)(x + 5) is a multiple of 9 for sure