Toán Lớp 8: 1)2x(x^2+1)-2x^3+x 2)(8x^3-1) :(2x-1) 3)(2x-1)(2x+1)-(x+2)(4x-3) 4)3xy^2(x^3-2xy^2+y)

Question

Toán Lớp 8:  1)2x(x^2+1)-2x^3+x  2)(8x^3-1) :(2x-1) 3)(2x-1)(2x+1)-(x+2)(4x-3) 4)3xy^2(x^3-2xy^2+y)

tuyethutanhthu · Answer

Giải đáp:       Lời giải và giải thích chi tiết:   $  1) 2x(x&sup2; + 1) - 2x&sup3; + x $   $  = 2x&sup3; + 2x - 2x&sup2; + x $   $  = 3x $   $  2) (8x&sup3; - 1) : (2x - 1) $   $  = [(2x - 1)(4x&sup2; + 2x + 1)] : (2x - 1) $   $  = 4x&sup2; + 2x + 1 $   $  3) (2x - 1)(2x + 1) - (x + 2)(4x - 3) $   $  = 4x&sup2; - 1 - (4x&sup2; - 3x + 8x - 6) $   $  = 4x&sup2; - 1 - 4x&sup2; + 3x - 8x + 6 $   $  = - 5x + 5 $   $  = - 5(x - 1) $   $  4) 3xy&sup2;(x&sup3; - 2xy&sup2; + y) $   $  = 3xy&sup2;.x&sup3; - 3xy&sup2;.2xy&sup2; + 3xy&sup2;.y $   $  = 3x^{4}y&sup2; - 6x&sup2;y^{4} + 3xy&sup3;  $

quynhthanhnghi · Answer

$1)2x(x^2+1)-2x^3+x$

$=2x^3+2x-2x^3+x$

$=(2x^3-2x^3)+(2x+x)$

$=3x$
$2)(8x^3-1):(2x-1)$

$=(2x-1)(4x^2+2x+1):(2x-1)$

$=4x^2+2x+1$

$3)(2x-1)(2x+1)-(x+2)(4x-3)$
$=4x^2-1-(4x^2-3x+8x-6)$

$=4x^2-1-4x^2+3x-8x+6$

$=-5x+5$

$=-5(x-1)$

$4)3xy^2(x^3-2xy^2+y)$

$=3xy^2.x^3-3xy^2.2xy^2+3xy^2.y$

$=3x^4y^2-6x^2y^4+3xy^3$

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