Answer:

1. PRIME

2. (b+2)(b+18)

3. (k-21)(k-2)

4. (x+4y)(x+6y)

5. (y-7x)^2

Answer:

1. Prime
2. (b + 18)(b + 2)
3. (k - 2)(k - 21)
4. (x + 6y)(x + 4y)
5. (y - 7x)²

Step-by-step explanation:

2. 36 + 20b + b²

b² + 20b + 36

b² + 18b + 2b + 36

b × (b + 18) + 2(b + 18)

= (b + 18)(b + 2)

3. 42 - 23k + k²

k² - 23k + 42

k² - 2k - 21k + 42

k × (k - 2) - 21(k - 2)

= (k - 2)(k - 21)

4. x² + 10xy + 24y²

x² + 6xy + 4xy + 24y²

x × (x + 6y) + 4y × (x + 6y)

= (x + 6y)(x + 4y)

5. y² - 14xy + 49x²

y² - 2 × y × 7x + 7²x²

y² - 2 × y × 7x + (7x)²

= (y - 7x)²