Question

cho A = ( 2x - 1 ) - ( 4x^2 + 2x + 1 ) - 7 . ( x^2 + 1 )

a/ rút gọn A

b/ tính A khi x = 1/2

Answer 1

a) `A=(2x-1)-(4x^2+2x+1)-7(x^2+1)`

`=2x-1-4x^2-2x-1-7x^2-7`

`=(-4x^2-7x^2)+(2x-2x)+(-1-1-7)`

`=-11x^2-9`

b) Thay `x=1/2` vào A ta có:

`A=-11*(1/2)^2-9`

`=-11/4-9=-47/4`

Answer 2

a)

b) Thay vào A ta có:

 

Answer 3

`a)` `A = (2x - 1) - (4x^2 + 2x + 1) - 7(x^2 + 1)`

`= 2x - 1 - 4x^2 - 2x - 1 - 7x^2 - 7`

`= (-4x^2 - 7x^2) + (2x - 2x) + (-1 - 1 - 7)`

`= -11x^2 - 9`

`b)` Với `x = 1/2`, ta có:

`A = -11 * (1/2)^2 - 9`

`= -11/4 - 9`

`= -47/4`.