Toán Lớp 8: Thực hiện phép tính:
a) 3x^2 .(2x^2-5x-4)
b) (x+1)^2 + (x-2)(x+3)-4x
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Toán Lớp 8: Thực hiện phép tính:
a) 3x^2 .(2x^2-5x-4)
b) (x+1)^2 + (x-2)(x+3)-4x
Comments ( 2 )
a) 3x² .(2x²-5x-4)
=$6x^{4}$ – $15x^{3}$ – 12²
b) (x+1)² + (x-2)(x+3)-4x
= x²+ 2x+1+ (x²+3x-2x-6) – 4x
= x² + 2x +1 + x² + 3x -2x -6 -4x
= 2x² -x -5
Giải đáp:
$a) 3x^2.(2x^2-5x-4)$
$= 3x^2.2x^2-3x^2.5x-3x^2.4$
$= 6x^4-15x^3-12x^2$
$b) (x+1)^2+(x-2).(x+3)-4x$
$= x^2+2x+1+x²+3x-2x-6-4x$
$= (x^2+x^2)+(2x+3x-2x-4x)+(1-6)$
$= 2x^2-x-5$