# If the coefficients of  and  are both zero , in the expansion of the expression  in powers of x , then the ordered pair ( a , b ) is equal to :  Option 1) (28, 861) Option 2) (-54 , 315 ) Option 3) ( 28, 315 ) Option 4) ( - 21 , 714 )

=

coefficient of

=>

=> b - 45 a +945 = 0..........................................(1)

coefficient of

=>

=> -b + 21 a -273 = 0 ........................................(2)

From (1) & (2)

a = 28 & b = 315

correct option (3).

Option 1)

(28, 861)

Option 2)

(-54 , 315 )

Option 3)

( 28, 315 )

Option 4)

( - 21 , 714 )

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