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a) \(x^4+324\)
\(=\left(x^2\right)^2+18^2+2.x^2.18-36x^2\)
\(=\left(x^2-18\right)^2-\left(6x\right)^2\)
\(=\left(x^2+18+6x\right)\left(x^2+18-6x\right)\)
b) \(64a^2+b^8\)
\(=\left(8a^2\right)^2+\left(b^4\right)^2+2.8a^2.4b^4-16a^2b^4\)
\(=\left(8a^2+b^4\right)^2-\left(ab^2\right)^2\)
\(=\left(8a^2+b^4+4ab^2\right)\left(8a^2+b^4-4ab^2\right)\)
\(a.\)
\(x^4+324\)
\(=\left(x^2\right)^2+18^2\)
\(=\left(x^2+18\right)\left(x^2_{ }-18\right)\)
\(b.\)
\(64a^2+b^8\)
\(=\left(8a^2\right)+\left(b^3\right)^2\)
\(\left(8a-b^3\right)\left(8a+b^3\right)\)
\(x^4+4\)
\(=x^4+4x^2+4-4x^2\)
\(=\left(x^2+2\right)^2-4x^2\)
\(=\left(x^2-2x+2\right)\left(x^2+2x+2\right)\)
\(x^4-4=\left(x^2\right)^2-2^2=\left(x^2-2\right)\left(x^2+2\right)\)
a, 4x4+1
=(2x)2+1
=(2x+1)(2x-1)
b,c tách làm bình phương rồi làm tương tự
x6+3x4y2-8x3y3+3x2y4+y6= x6+3x4y2+3x2y4+y6-8x3y3=(x2+y2)3-(2xy)3
= (x2+y2-2xy)[(x2+y2)2+2xy(x2+y2)+(2xy)2]= (x-y)2(x4+6x2y2+y4+2x3y+2xy3)
(x2+y2-5)2-4x2y2-16xy-16=(x2+y2-5)2-(4x2y2+16xy+16)=(x2+y2-5)2-(2xy+4)2
=(x2+y2-5+2xy+4)(x2+y2-5-2xy-4)=(x2+2xy+y2-1)(x2-2xy+y2-9)=[(x+y)2-1][(x-y)2-32]=(x+y-1)(x+y+1)(x-y-3)(x-y+3)
x4+324=x4+36x2+324-36x2=(x2+18)2-(6x)2=(x2+18-6x)(x2+18+6x)
#)Giải :
\(x^3-2x-4\)
\(=x^3+2x^2-2x^2+2x-4x-4\)
\(=x^3+2x^2+2x-2x^2-4x-4\)
\(=x\left(x^2+2x+2\right)-2\left(x^2+2x+2\right)\)
\(=\left(x-2\right)\left(x^2+2x+2\right)\)
\(x^4+2x^3+5x^2+4x-12\)
\(=x^4+x^3+6x^2+x^3+x^2+6x-2x^2-2x-12\)
\(=x^2\left(x^2+x+6\right)+x\left(x^2+x+6\right)-2\left(x^2+x+6\right)\)
\(=\left(x^2+x+6\right)\left(x^2+x-2\right)\)
\(=\left(x^2+x+6\right)\left(x-1\right)\left(x+2\right)\)
Câu 1.
Đoán được nghiệm là 2.Ta giải như sau:
\(x^3-2x-4\)
\(=x^3-2x^2+2x^2-4x+2x-4\)
\(=x^2\left(x-2\right)+2x\left(x-2\right)+2\left(x-2\right)\)
\(=\left(x-2\right)\left(x^2+2x+2\right)\)
a) \(x^4+324=\left(x^2-6x+18\right)\left(x^2+6x+18\right)\)
c) \(x^{13}+x^5+1=\left(x^2+x+1\right)\left(x^{11}-x^{10}+x^8-x^7+x^5-x^4+x^3-x+1\right)\)
d) \(x^{11}+x+1=\left(x^2+x+1\right)\left(x^9-x^8+x^6-x^5+x^3-x^2+1\right)\)
e) \(x^8+3x^4+4=\left(x^4+x^2+2\right)\left(x^4-x^2+2\right)\)
x^4+324
=x4+36x2+324-36x2
=(x2+18)2-36x2
=(x2-6x+18)(x2+6x+18)