Đáp án:
a/ $4+4xy+x^2y^2$
b/ $25-30x+9x^2$
c/ $25-x^4$
d/ $125x^3-75x^2+15x-1$
e/ $8x^3-y^3$
f/ $x^3+27$
g/ $x^3+64$
h/ $x^6-\frac{1}{27}$
i/ $a^2+b^2+c^2+2ab+2ac+2bc$
j/ $a^2+b^2+c^2+2ab-2ac-2bc$
Giải thích các bước giải:
a/ $(2+xy)^2=2^2+2.2xy+(xy)^2=4+4xy+x^2y^2$
b/ $(5-3x)^2=5^2-2.5.3x+(3x)^2=25-30x+9x^2$
c/ $(5-x^2)(5+x^2)=5^2-(x^2)^2=25-x^4$
d/ $(5x-1)^3=(5x)^3-3.(5x)^2+3.5x-1=125x^3-75x^2+15x-1$
e/ $(2x-y)(4x^2+2xy+y^2)=(2x)^3-y^3=8x^3-y^3$
f/ $(x+3)(x^2-3x+9)=x^3+3^3=x^3+27$
g/ $(x+4)(x^2-4x+16)=x^3+4^3=x^3+64$
h/ `(x^2-\frac{1}{3})(x^4+\frac{1}{3}x^2+\frac{1}{9})=(x^2)^3-(\frac{1}{3})^3=x^6-\frac{1}{27}`
i/ $(a+b+c)^2$
$=(a+b)^2+2(a+b)c+c^2$
$=a^2+2ab+b^2+2ac+2bc+c^2$
$=a^2+b^2+c^2+2ab+2bc+2ac$
j/ $(a+b-c)^2$
$=(a+b)^2-2(a+b)c+c^2$
$=a^2+2ab+b^2-2ac-2bc+c^2$
$=a^2+b^2+c^2+2ab-2ac-2bc$
Chúc bạn học tốt !!!
