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\(\left(x+a\right)\left(x+2a\right)\left(x+3a\right)\left(x+4a\right)+a^4.\)
\(=\left(x+a\right)\left(x+4a\right)\left(x+2a\right)\left(x+3a\right)+a^4.\)
\(=\left(x^2+5ax+4a^2\right)\left(x^2+5ax+6a^2\right)+a^4.\)
\(=\left(x+5ax+4a^2+a^2\right)^2.\)
\(=\left(x+5ax+5a^2\right)^2.\)
\(\left(x+a\right)\left(x+2a\right)\left(x+3a\right)\left(x+4a\right)+a^4\)
\(=\)\(\left(x+a\right)\left(x+4a\right)\left(x+2a\right)\left(x+3a\right)+a^4\)
\(=\)\(\left(x^2+5ax+4a^2\right)\left(x^2+5ax+6a^2\right)+a^4\)
\(=\)\(\left[\left(x^2+5ax+5a^2\right)-a^2\right].\left[\left(x^2+5ax+5a^2\right)-a^2\right]+a^4\)
\(=\)\(\left(x^2+5ax+5a^2\right)^2-a^4+a^4\)
\(=\)\(\left(x^2+5ax+5a^2\right)^2\)
Chúc bạn học tốt ~
(x + a)(x + 2a)(x + 3a)(x + 4a) + a4
= (x + a)(x + 4a)(x + 2a)(x + 3a) + a4
= (x2 + 4ax + ax + 4a2)(x2 + 3ax + 2ax + 6a2) + a4
= (x2 + 5ax + 4a2)(x2 + 5ax + 6a2) + a4
Đặt x2 + 5ax + 4a2 = t
= t(t + 2a2) + a4
= (t + a2)2
= (x2 + 5ax + 4a2 + a2)2
= (x2 + 5ax + 5a2)2
b. \(\left(a^2+a\right)+a\left(a^2+a\right)-12\)
<=>\(\left(x^3+3x^2-4\right)+\left(3x^2+9x-12\right)\)
<=>\(x\left(x^2+3x-4\right)+3\left(x^2+3x-4\right)\)
<=>\(\left(x^2+3x-4\right)\left(x+3\right)\)
<=>\(\left(x+3\right)\left(x^2+4x\right)-\left(x-4\right)\)
đóngmở ngoặc nhé mk ngại ghi lại
<=>(x+3)(x(x+4)-(x+4))
<=>(x+3)(x-1)(x+4)
kết pn fb mk nhé longtrangv@gmail.com
c) \(x^3-x^2-4x^2+8x-4\)
= \(x^3-x^2-4x^2+4x+4x-4\)
= \(x^2\left(x-1\right)-4x\left(x-1\right)+4\left(x-1\right)\)
= \(\left(x-1\right)\left(x^2-4x+4\right)\)
= \(\left(x-1\right)\left(x-2\right)^2\)
Ta có:\(b^4+4a^4=b^4+4a^2b^2+4a^4-4a^2b^2\)
\(=\left(a^2\right)^2+2.a^2.\left(2b^2\right)+\left(2b^2\right)^2-\left(2ab\right)^2\)
\(=\left(a^2+2b^2\right)^2-\left(2ab\right)^2\)
\(=\left(a^2-2ab+2b^2\right)\left(a^2+2ab+2b^2\right)\)
\(x^8+x^4-2\)
\(=\left(x^8-1\right)+\left(x^4-1\right)\)
\(=\left(x^4+1\right)\left(x^4-1\right)+\left(x^4-1\right)\)
\(=\left(x^4-1\right)\left(x^4+2\right)=\left(x^2-1\right)\left(x^2+1\right)\left(x^4+2\right)\)
\(x^4+4=\left(x^2\right)^2+2^2\)
\(=\left(x^2+2\right)^2-2.x^2.2=\left(x^2+2\right)^2-\left(2x\right)^2\)
\(=\left(x^2+2x+2\right)\left(x^2-2x+2\right)\)
\(A=x^4+x^2+1\)
\(=x^4-x+x^2+x+1\)
\(=x\left(x^3-1\right)+\left(x^2+x+1\right)\)
\(=x\left(x-1\right)\left(x^2+x+1\right)+\left(x^2+x+1\right)\)
\(=\left(x^2-x+1\right)\left(x^2+x+1\right)\)
`(x - a)^4 + 4a^4`
`= [(x-a)^4 + 4a^2(x - a)^2 + 4a^4)] - 4a^2(x - a)^2`
`= [(x - a)^2 + 2a^2]^2 - [2a(x - a)]^2`
`= [(x - a)^2 +2a^2 - 2a(x - a)].[(x - a)^2 + 2a^2 + 2a^2+2a(x - a)`
`= (x^2 - 2ax + a^2 + 2a^2 - 2ax + 2a^2).(x^2 - 2ax + a^2 + 2a^2 + 2ax - 2a^2)`
`= (x^2 - 4ax + 5a^2)(x^2 + a^2)`
ok
\(\left(x-a\right)^4+4a^4\)
=\(\left\lbrack\left(x-a\right)^2\right\rbrack^2+2.2a^2.\left(x-a\right)^2+\left(2a^2\right)^2-2.2a^2.\left(x-a\right)^2\)
\(=\left\lbrack\left(x-a\right)^2+2a^2\right\rbrack^2-4a^2\left(x-a\right)^2\)
\(=\left\lbrack\left(x-a\right)^2+2a^2\right\rbrack^2-\left(2ax-2a^2\right)^2\)
=\(\left\lbrack\left(x-a\right)^2+2a^2-2ax+2a^2\right\rbrack\left\lbrack\left(x-a\right)^2+2a^2+2ax-2a^2\right\rbrack\)
=\(\left(x^2-4ax+5a^2\right)\left(x^2+a^2\right)\)