Question

Who know answer only they will give answers. And who don't know and still giving answer. Then I report his or her answer. THANK YOU. Question no. 17, 18, 19.

Answer 1

17. ( x + y )³ - ( x³ + y³ )

= ( x + y )³ - ( x + y ) ( x² + y² - xy )

= ( x + y ) { ( x + y )² - x² - y² + xy }

= ( x + y ) ( x² + y² + 2xy - x² - y² + xy )

= ( x + y ) ( 3xy )

Option(d) 3xy.

18. ( x + 3 )³

= ( x )³ + 3³ + 3x²  × 3 + 3 x × 3²

= x³ + 9 + 9x² + 27x

So, coefficient of x is 27.

Option ( d ) 27.

19.

Given,

⇒ ( x/y ) + ( y/x ) = -1

      x² + y²
⇒ _________  = -1

         xy
∴ x² + y² = -xy

Now,

= ( x³ - y³ )

= ( x - y ) ( x² + y² + xy )

= ( x + y ) ( -xy + xy )

= ( x + y ) 0

= 0

Option ( c ) 0.