Question

Solve using the appropriate identities (a) ( 3x -4) ( 3x+4). (b) (2x-7y)² (c) (3x+4y)²​

Answer 1

Step-by-step explanation:

(a) (3x-4)(3x+4)

= (a-b)(a+b)=a-b

= (3x)²-(4)²

= 9x²-16

(b) (2x-7y)²

= (a-b)²= a²+b²-2ab

= 4x²+49y²-28xy

(c) (3x+4y)²

= (a+b)²= a²+b²+2ab

= 9x²+16y²+24xy

Hope it helps :)

Answer 2

Answer:

(a) (3x-4)(3x+4)

= (3x)² - (4)²

= 9x² - 16

Identity used : (a-b)(a+b) = a² - b²

(b) (2x-7y)²

= (2x)² + (7y)² - 2(2x)(7y)

= 4x² + 49y² - 28xy

Identity used : (a-b)² = a² + b² - 2ab

(c) (3x+4y)²​

= (3x)² + (4y)² + 2(3x)(4y)

= 9x² + 16y² + 24xy

Identity used : (a+b)² = a² + b² + 2ab