THực hiện phép tính :
a) ( 5x – 2y ) ( x^2 – xy + 1 )
b) ( x – 1 ) ( x + 1 ) ( x + 2 )
c) 1/2 x^2y^2 ( 2x + y ) ( 2x – y )
d) ( 1/2x – 1 ) ( 2x – 3 )
e) ( x – 7 ) ( x – 5 )
f) ( x – 1/2 ) ( x + 1/2 ) ( 4x – 1 )
THực hiện phép tính :
a) ( 5x – 2y ) ( x^2 – xy + 1 )
b) ( x – 1 ) ( x + 1 ) ( x + 2 )
c) 1/2 x^2y^2 ( 2x + y ) ( 2x – y )
d) ( 1/2x – 1 ) ( 2x – 3 )
e) ( x – 7 ) ( x – 5 )
f) ( x – 1/2 ) ( x + 1/2 ) ( 4x – 1 )
Đáp án:
Giải thích các bước giải:
a/ $(5x-2y)(x^2-xy+1)$
$=5x^3-2x^2y-5x^2y+2xy^2+5x-2y$
$=5x^3-7x^2y+2xy^2+5x-2y$
b/ $(x-1)(x+1)(x+2)$
$=(x^2-1)(x+2)$
$=x^3-x+2x^2-2$
$=x^3+2x^2-x-2$
c/ $\frac{1}{2}.x^2y^2.(2x+y)(2x-y)$
$=\frac{1}{2}.x^2y^2.(4x^2-y^2)$
$=2x^4y^2-\frac{1}{2}x^2y^4$
d/ $(\frac{1}{2}x-1)(2x-3)$
$=x^2-2x-\frac{3}{2}x+3$
$=x^2-\frac{7}{2}x+3$
e/ $(x-7)(x-5)$
$=x^2-7x-5x+35$
$=x^2-12x+35$
f/ $(x-\frac{1}{2})(x+\frac{1}{2})(4x-1)$
$=(x^2-\frac{1}{4})(4x-1)$
$=4x^3-x-x^2+\frac{1}{4}$
$=4x^3-x^2-x+\frac{1}{4}$
Chúc bạn học tốt !!