Question

The coefficient of ab in the expansion of (3a-2b)² is​

Answer 1

Answer:

-12

Step-by-step explanation:

(3a-2b)²

(3a)²+(2b)-2×3a×2b

9a²+4b²-12ab

so,the coefficient is -12.

Answer 2

The coefficient of ab in expansion of (3a-2b)² is​ -12

Given: The expansion of (3a-2b)²

To find: The coefficient of ab in expansion of  (3a-2b)²  

Solution:  

To expand (3a-2b)² we will use the identity (x - y)² = x² + y² - 2xy

Now assume x = 3a, y = 2b and expand (3a-2b)²

⇒  (3a-2b)² = (3a)² + (2b)² - 2(3a)(2b)  

= 9a² + 4b² - 12ab  

Here coefficient refers the numeric value which is multiplied by a variable

Example: In 2a, 2 is the coefficient of a

               In 5xy, 5 is the coefficient of xy  

In 9a² + 4b² - 12ab, coefficient of ab is -12

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