Câu 1:
(3x+1)2_(x-2)2
=[(3x)2+2×3x×1+13]-[x2+2×x×2+22]
=(9x2+6x+1)-(x2+4x+4)
=9x2+6x+11-x2-4x-4
Câu 2 :
(y-3)2-(y-1)2
=(y2-2×y×3+32)-(y2+2×y×1+1)
= y2-6y+99-y2-2y-1
1.(3x+1)^2-(x-2)^2
=(3x+1+x-2)(3x+1-x+2)
=(4x-1)(2x+3)=8x^2+12x-2x-3
=8x^2+10x-3y
2.(y-3)^2-(y-1)^2
=(y-3+y-1)(y-3-y+1)
=(2x-4)(-2)
=-4x+8
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