Question

Multiply ( 3x + 4y ) and ( 2x - 7y )​

Answer 1

$\sf QUESTION -$

Multiply ( 3x + 4y ) and ( 2x - 7y )

⠀

$\sf REQUIRED \: ANSWER -$

6x² – 13xy – 28y²

⠀

$\sf SOLUTION -$

[ Note - this question can be done by two methods ]

Horizontal method : -

(3x + 4y) × (2x – 7y)

= 3x × (2x – 7y) + 4y × (2x - 7y)

= 3x × 2x - 3x × 7y + 4y × 2x - 4y × 7y

= 6x² - 21xy + 8xy – 28y²

= 6x² – 13xy – 28y²

⠀

Column method : -

⠀3x + 4y

× 2x - 7y

________⠀⠀⠀⠀⠀[Multiplying by 2]

6x² + 8xy

⠀⠀ - 21xy - 28y² ⠀[Multiplying by -7y]

_____________

6x² - 13xy - 28y²⠀ [Adding]

_____________