Câu 1 :
a ) ( x – 2y ) ²
b ) ( 2x ² + 3 ) ²
c ) ( x – 2 ) ( x ² + 2x + 4 )
d ) ( 2x – 1 ) ³
Câu 1 : a ) ( x – 2y ) ² b ) ( 2x ² + 3 ) ² c ) ( x – 2 ) ( x ² + 2x + 4 ) d ) ( 2x – 1 ) ³
By Arianna
By Arianna
Câu 1 :
a ) ( x – 2y ) ²
b ) ( 2x ² + 3 ) ²
c ) ( x – 2 ) ( x ² + 2x + 4 )
d ) ( 2x – 1 ) ³
Đáp án:
`a)`$(x-2y)^2$
$=x^2-2.2y+(2y)^2$
$=x^2-4y+4y^2$
`b)`$(2x^2+3)^2$
$=(2x^2)^2+2.2x^2. 3+3^2$
$=4x^4+12x^2+9$
`c)` $(x-2)(x^2+2x+4)$
$=x^3-2^3$
$=x^3-8$
`d)`$(2x-1)^3$
$=(2x)^3-3.(2x)^2. 1+3.2x.1^2-1^2$
$=8x^3-12x^2+6x-1$
Đáp án:
a,
$(x-2y)^2$
$=x^2-2·2y+(2y)^2$
$=x^2-4y+4y^2$
b,
$(2x^2+3)^2$
$=(2x^2)^2+2·2x^2·3+3^2$
$=4x^4+12x^2+9$
c,
$(x-2)(x^2+2x+4)$
$=(x-2)(x^2+x·2+2^2)$
$=x^3-2^3$
$=x^3-8$
d,
$(2x-1)^3$
$=(2x)^3-3·(2x)^2·1+3·2x·1^2-1^2$
$=8x^3-12x^2+6x-1$