The y-intercept is 4 because it is the only number without a variable
Answer: 
Step-by-step explanation:

Answer:
(4a + 7b)(16a² - 28ab + 49b²)
Step-by-step explanation:
Use the sum of two cubes to factor
In addition
a³ + b³ = (a + b)(a² - ab + b²)
In subtraction
a³ - b³ = (a - b)(a² + ab + b²)
64a³ + 343b³ = (4a + 7b)(16a² - 28ab + 49b²)