Question

Expand (3a+2b-7c)² using algebric identities pls help​

Answer 1

Step-by-step explanation:

(3a)²+(2b)²+(-7c)²+2(3a)(2b) +2(2b)(-7c)+2(-7c)(3a)

9a²+4b²+49c²+12ab-28bc-42ca

Answer 2

Answer:

9a² + 4b² + 49c² + 12ab - 28bc - 42ac

Step-by-step explanation:

Here, for solving this question we apply this identity:

(a + b + c)² = a² + b² + c² + 2(ab + bc + ac)

where:

• a = 3a
• b = 2b
• c = -7c

Put in these values in the above mentioned identity.

(3a + 2b - 7c)²

= (3a)² + (2b)² + (-7c)² + 2[(3a)(2b) + (2b)(-7c) + (-7c)(3a)]

= 9a² + 4b² + 49c² + 2[6ab - 14bc - 21ac]

= 9a² + 4b² + 49c² + 12ab - 28bc - 42ac

∴ (3a+2b-7c)²

=【9a² + 4b² + 49c² + 12ab - 28bc - 42ac】

KNOW MORE:

Some important algebraic identities:

1. (a + b)² = a² + b² + 2ab
2. (a - b)² = a² + b² - 2ab
3. a² - b² = (a + b) (a - b)
4. (a + b)³ = a³ + b³ + 3ab(a + b)