Đáp án+Giải thích các bước giải:
a, Sửa đề chút
$P=(5x-1)^2+2(1-5x)(4+5x)+(5x+4)^2$
$=(5x-1)^2-2(5x-1)(5x+4)+(5x+4)^2$
$=(5x-1-5x-4)^2$
$=25$
b,
$Q=(x-y)^3+(y+x)^3+(y-x)^3-3xy(x+y)$
$=(x-y)^3+(y+x)^3-(x-y)^3-3xy(x+y)$
$=x^3+3x^2y+3xy^2+y^3-3x^2y-3xy^2$
$=x^3+y^3$
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a,
$P=(5x-1)+2(1-5x)(4+5x)+(5x+4)^2$
$=5x-1+(2-10x)(4+5x)+25x^2+40x+16$
$=5x-1+8+10x-40x-50x^2+25x^2+40x+16$
$=-25x^2+15x+23$
