Answer: 2x − 5y / 2x + 5y
Step-by-step explanation:
8x^3 − 125y^3/(2x + 5y)3 ÷ 4x^2 + 10xy + 25y^2/4x^2 + 20xy + 25y^2
To divide by a fraction, multiply by its reciprocal.
8x^3 − 125y^3/(2x + 5y)^3 ⋅ 4x^2 + 20xy + 25y^2/4x^2 + 10xy + 25y^2
Simplify the numerator.
Rewrite 8x^3 as (2x)^3.
(2x)^3 − 125y^3/(2x + 5y)^3 ⋅ 4x^2 + 20xy + 25y^2/4x^2 + 10xy + 25y^2
Rewrite 125y^3 as (5y)^3.
(2x)^3 − (5y)^3/(2x + 5y)^3 ⋅ 4x^2 + 20xy + 25y^2/4x^2 + 10xy + 25y^2
Since both terms are perfect cubes, factor using the difference of cubes formula,
a^3 − b^3 = (a − b) (a^2 + ab + b^2) where a = 2x and b = 5y.
(2x − (5y)) ((2x)^2 + 2x (5y) + (5y)^2)/(2x + 5y)^3 ⋅ 4x + 20xy + 25y^2/ 4x^2 + 10xy + 25y^2
Multiply 5 by −1.
(2x − 5y) ((2x)^2 + 2x (5y) + (5y)^2)/(2x + 5y)^3 ⋅ 4x^2 + 20xy + 25y^2/4x^2 + 10xy + 25y^2
Apply the product rule to 2x.
(2x − 5y) (22x^2 + 2x (5y) + (5y)^2)/(2x + 5y)3 ⋅ 4x^2 + 20xy + 25y^2/4x^2 + 10xy + 25y2
Raise 2 to the power of 2.
(2x − 5y) (4x^2 + 2x (5y) + (5y)^2)/(2x + 5y)^3 ⋅ 4x^2 + 20xy + 25y^2/4x^2 + 10xy + 25y^2
Rewrite using the commutative property of multiplication.
(2x − 5y) (4x^2 + 2 ⋅ 5xy + (5y)^2)/(2x + 5y)^3 ⋅ 4x^2 + 20xy + 25y^2/4x^2 + 10xy + 25y^2
Multiply 2 by 5.
(2x − 5y) (4x^2 + 10xy + (5y)^2)/(2x + 5y)^3 ⋅ 4x^2 + 20xy + 25y^2/ 4x^2 + 10xy + 25y^2
Apply the product rule to 5y.
(2x − 5y) (4x^2 + 10xy + 52y^2)/(2x + 5y)^3 ⋅ 4x^2 + 20xy + 25y^2/4x^2 + 10xy + 25y^2
Raise 5 to the power of 2.
(2x − 5y) (4x^2 + 10xy + 25y^2)/(2x + 5y)^3 ⋅ 4x^2 + 20xy + 25y^2/4x^2 + 10xy + 25y^2
Cancel the common factor of 4x^2 + 10xy + 25y^2.
((2x − 5y)/(2x + 5y)^3) (4x^2 + 20xy + 25y^2)
Multiply
(2x − 5y) (4x^2 + 20xy + 25y^2)/ (2x + 5y)^3
Factor using the perfect square rule.
Rewrite 4x^2 as (2x)^2.
(2x − 5y) ((2x)^2 + 20xy + 25y^2)/ (2x + 5y)^3
Rewrite 25y^2 as (5y)^2.
(2x − 5y) ((2x)^2 + 20xy + (5y)^2)/ (2x + 5y)^3
Check that the middle term is two times the product of the numbers being squared in the first
term and third term.
20xy = 2 ⋅ (2x) ⋅ (5y)
Rewrite the polynomial.
(2x − 5y) ((2x)2 + 2 ⋅ (2x) ⋅ (5y) + (5y)2)/(2x + 5y)^3
Factor using the perfect square trinomial rule a^2 + 2ab + b^2 = (a + b)^2, where a = 2x and b = 5y.
(2x − 5y) (2x + 5y)^2/ (2x + 5y)^3
Cancel the common factor of (2x + 5y)^2 and (2x + 5y)^3.
Factor (2x + 5y)^2 out of (2x − 5y) (2x + 5y)^2.
(2x + 5y)^2 (2x − 5y) / (2x + 5y)^3
Cancel the common factors.
2x − 5y / 2x + 5y
