write the identity of a³+b³
Answers
Answer:
Here, volume is in cubic units. Hence, a³-b³ = (a-b) (a²+ab+b²). The algebraic identity a³-b³ = (a-b) (a²+ab+b²) has been verified.
Step-by-step explanation:
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Identities :-
- (a+b)² = a² + 2ab + b²
- (a-b)² = a² - 2ab + b²
- (a+b+c)² = a² + b² + c² + 2ab + 2bc + 2ca
- (x+a)(x+b) = x² + x(a+b) + ab
- a²-b² = (a+b)(a-b)
- (a+b)³ = a³ + 3a²b + 3ab² + b³
- (a-b)³ = a³ - 3a²b + 3ab² - b³
- a³+b³ = (a+b)(a² - ab + b²)
- a³-b³ = (a-b)(a² + ab + b²)
- a³+b³+c³ - 3abc = (a+b+c)(a² + b² + c² - ab - bc - ca)
Conditional identity:-
if a + b + c = 0,
then,
- a³ + b³ + c³ = 3abc
Examples :-
(a+b)² = a² + 2ab + b²
- a = 2
- b = 1
Substituting,
=≥ (2)² + 2(2)(1) + 1²
=≥ 4 + 4 + 1
=≥ 9
(a-b)² = a² - 2ab + b²
- a = 2
- b = 1
Substituting,
=≥ (2)² - 2(2)(1) + (1)²
=≥ 4 - 4 + 1
=≥ 1
(a+b+c)² = a² + b² + c² + 2(ab + bc + ca)
- a = 2
- b = 1
- c = 3
Substituting,
=≥ (2)² + (1)² + (3)² + 2[(2)(1) + (1)(3) + (3)(2)]
=≥ 4 + 1 + 9 + 2(2 + 3 + 6)
=≥ 14 + 2(11)
=≥ 14 + 22
=≥ 36
(x+a)(x+b) = x² + x(a+b) + ab
- a = 2
- b = 1
- x = 3
Substituting,
=≥ (3)² + 3(1+2) + (1)(2)
=≥ 9 + 3(3) + 2
=≥ 9 + 9 + 2
=≥ 20
a²-b² = (a+b)(a-b)
- a = 2
- b = 1
Substituting,
=≥ (2-1)(2+1)
=≥ (1)(3)
=≥ 3
(a+b)³ = a³ + 3ab(a+b) + b³
- a = 2
- b = 1
Substituting,
=≥ (2)³ + 3(2)(1)(2+1) + (1)³
=≥ 8 + 6(3) + 1
=≥ 8 + 18 + 1
=≥ 27
(a-b)³ = a³ - 3ab(a-b) - b³
- a = 2
- b = 1
Substituting,
=≥ (2)³ - 3(2)(1)(2-1) - (1)³
=≥ 8 - 6(1) - 1
=≥ 8 - 6 - 1
=≥ 1
a³+b³ = (a+b)(a² - ab + b²)
- a = 2
- b = 1
Substituting,
=≥ 2³ + 1³
=≥ (2+1)(2² - (2)(1) + 1²)
=≥ (3)(4 - 2 + 1)
=≥ 3(3)
=≥ 9
a³-b³ = (a-b)(a² + ab + b²)
- a = 2
- b = 1
Substituting,
=≥ 2³ - 1³
=≥ (2-1)(2² + (2)(1) + 1²)
=≥ (1)(4 + 2 + 1)
=≥ (1)(7)
=≥ 7
a³+b³+c³ - 3abc = (a+b+c)(a² + b² + c² - ab - bc - ca)
- a = 2
- b = 1
- c = 3
Substituting,
=≥ (2)³ + (1)³ + (3)³ - 3(2)(1)(3)
=≥ (2+1+3)[2² + 1² + 3² - (2)(1) - (1)(3) - (3)(2)]
=≥ (6)(4 + 1 + 9 - 2 - 3 - 6)
=≥ 6(14 - 11)
=≥ 6(3)
=≥ 18
Conditional identity :-
if a + b + c = 0,
then
a³ + b³ + c³ = 3abc
- a = 2
- b = 1
- c = (-3)
Substituting,
=≥ 2 + 1 + (-3)
=≥ 3 + (-3)
=≥ 0
Hence,
=≥ (2)³ + (1)³ + (-3)³
=≥ 3(2)(1)(-3)
=≥ (-18)