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222-9+11+12:2*14+14 = ? ( )

## Toán Lớp 8: Bài 1. Tính a ) 6x^2 – 4x^2 (x^2 – 3x – 2 ) . b ) ( 3x – 2)^2 – 2(x – 1 )^2 . c ) ( 2x^4 + 5x + x^3 – 2 – 2 – 3x^2 ) : ( x^2 + 1 –

Toán Lớp 8: Bài 1. Tính
a ) 6x^2 – 4x^2 (x^2 – 3x – 2 ) .
b ) ( 3x – 2)^2 – 2(x – 1 )^2 .
c ) ( 2x^4 + 5x + x^3 – 2 – 2 – 3x^2 ) : ( x^2 + 1 – x )

## Comments ( 2 )

1. Giải đáp + Lời giải và giải thích chi tiết:
a)
6x^2-4x^2(x^2-3x-2)
=6x^2-4x^4+12x^3+8x^2
=-4x^4+12x^3+(6x^2+8x^2)
=-4x^4+12x^3+14x^2
b)
(3x-2)^2-2(x-1)^2
=9x^2-12x+4-2(x^2-2x+1)
=9x^2-12x+4-2x^2+4x-2
=(9x^2-2x^2)-(12x-4x)+4-2
=7x^2-8x+2
c) Xem hình

2. a) 6x^2 – 4x^2(x^2 – 3x – 2)
= 6x^2 – (4x^4 – 12x^3 – 8x^2)
= 6x^2 – 4x^4 + 12x^3 + 8x^2
= 14x^2 – 4x^4 + 12x^3
b) (3x-2)^2 – 2(x-1)^2
= 9x^2 – 12x + 4 – 2(x^2 – 2x + 1)
= 9x^2 – 12x + 4 – 2x^2 + 4x -2
= 7x^2 – 8x + 2
c)  ( 2x^4 + 5x + x^3 – 2 – 2 – 3x^2 ) : ( x^2 + 1 – x )