Given:
The given expression = (a−2b)3+(2b−4c)3+(4c−a)3(a2−4b2)3+64(b2−4c2)3+(16c2−a2)3
Formula used:
If a + b + c = 0 then a3 + b3 + c3 = 3abc
Calculation:
(a−2b)3+(2b−4c)3+(4c−a)3(a2−4b2)3+64(b2−4c2)3+(16c2−a2)3
= (a−2b)3+(2b−4c)3+(4c−a)3(a2−4b2)3+(4b2−16c2)3+(16c2−a2)3
Let, a2 - 4b2 = x; 4b2 - 16c2 = y; 16c2 - a2 = z
Here, x + y + z = a2 - 4b2 + 4b2 - 16c2 + 16c2 - a2 = 0
Then, (a2 - 4b2)3 + (4b2 - 16c2)3 + (16c2 - a2)3 = 3 (a2 - 4b2) (4b2 - 16c2) (16c2 - a2)
Let, a - 2b = p; 2b - 4c = q; 4c - a = r
Here, p + q + r = a - 2b + 2b - 4c + 4c - a = 0
Then, (a - 2b)3 + (2b - 4c)3 + (4c - a)3 = 3 (a - 2b) (2b - 4c) (4c - a)
Now, (a−2b)3+(2b−4c)3+(4c−a)3(a2−4b2)3+(4b2−16c2)3+(16c2−a2)3 = 3(a−2b)(2b−4c)(4c−a)3(a2−4b2)(4b2−16c2)(16c2−a2)
= (a−2b)(2b−4c)(4c−a)(a+2b)(a−2b)(2b+4c)(2b−4c)(4c+a)(4c−a) [Using a2 - b2 = (a + b) (a - b) formula]
= (a + 2b) (2b + 4c) (4c + a)
= 2 (a + 2b) (b + 2c) (4c + a)
∴ The value of the expression is 2 (a+ 2b) (b + 2c) (4c + a)
Alternate Method (a−2b)3+(2b−4c)3+(4c−a)3(a2−4b2)3+64(b2−4c2)3+(16c2−a2)3
We know that a + b + c = 0 then a3 + b3 + c3 = 3abc
First, we satisfy the numerator and denominator with this equation.
⇒ (a2 - 4b2) + (4b2 - 16c2) + (16c2 - a2) = 0
Now, (a - 2b) + (2b - 4c) + (4c - a) = 0
(a−2b)3+(2b−4c)3+(4c−a)3(a2−4b2)3+64(b2−4c2)3+(16c2−a2)3
⇒ 3(a−2b)(2b−4c)(4c−a)3(a2−4b2)(4b2−16c2)(16c2−a2) = (a−2b)(2b−4c)(4c−a)(a−2b)(a+2b)(2b−4c)(2b+4c)(4c−a)(4c+a)
⇒ (a + 2b){2(b + 2c)}(4c + a)
⇒ 2(a + 2b)(b + 2c)(4c + a)
∴ The value of the expression is 2(a + 2b)(b + 2c)(4c + a).