Phân tích đa thức thành nhân tử (3 phg pháp đầu) MÌNH CẦN GẤP Ạ GIÚP MÌNH VỚI
a. \(4x^2\) - \(40x^4\) +\(100x^3\)
b. 3xy.(x-5)-7x+35
c. \(a^2\) - am - \(b^2\) -bm
d. \(x^3\)- 4x - \(x^2y\) + 4y
e. \(x^3 + 6x^2\) 12x +8
f. \(a^3 - 2a^2-ab^2+2b^2\)
g. \(2a^2x - 2a^2 - 2abx +4ab - 2b^2\)
h. \(x^2 - 2xy+ y^2 -25\)
a)
$4x^2-40x^4+100x^3=4x^2(1-10x^2+25x)$
b)
\(3xy(x-5)-7x+35=3xy(x-5)-7(x-5)\)
\(=(x-5)(3xy-7)\)
c)
\(a^2-am-b^2-bm=(a^2-b^2)-(am+bm)=(a-b)(a+b)-m(a+b)\)
\(=(a+b)(a-b-m)\)
d)
\(x^3-4x-x^2y+4y=(x^3-x^2y)-(4x-4y)\)
\(=x^2(x-y)-4(x-y)=(x^2-4)(x-y)=(x-2)(x+2)(x-y)\)
e)
$x^3+6x^2+12x+8=x^3+3.2.x^2+3.2^2.x+2^3=(x+2)^3$
f)
$a^3-2a^2-ab^2+2b^2=(a^3-ab^2)-(2a^2-2b^2)$
$=a(a^2-b^2)-2(a^2-b^2)=(a^2-b^2)(a-2)=(a-b)(a+b)(a-2)$
g)
$2a^2x-2a^2-2abx+4ab-2b^2=(2a^2x-2abx)-(2a^2-4ab+2b^2)$
$=2ax(a-b)-2(a-b)^2=2(a-b)(ax-a+b)$
h)
\(x^2-2xy+y^2-25=(x-y)^2-25=(x-y)^2-5^2=(x-y+5)(x-y-5)\)
