Answer:
531.
Step-by-step explanation:
Let's assume 2(1) + 1 = 3
a = 1 and b = 1
Now we can plug that in
8(1)^3 + (1)^3 + 18(1)(1)
Then we need to multiply together
8^3 + 1^3 + 18
Then do the powers
512 + 1 + 18
Then add them together
531
Hope this helped!
Answer:
27
Step-by-step explanation:
A sum of cubes factors as
a³ + b³ = (a + b)(a² - ab + b²)
Factor the sum of cubes 8a³ + b³
8a³ = (2a)³, thus
8a³ + b³
= (2a)³ + b³
= (2a + b)(4a² - 2ab + b²)
We now have the right side as
(2a + b)(4a² - 2ab + b²) + 18ab ← substitute 2a + b = 3
= 3(4a² - 2ab + b²) + 18ab
= 12a² - 6ab + 3b² + 18ab ← collect like terms
= 12a² + 12ab + 3b² ← factor out 3 from each term
= 3(4a² + 4ab + b²) ← perfect square
= 3(2a + b)² ← substitute 2a + b = 3
= 3 × 3²
= 3 × 9
= 27
