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A=x^4+6x^3+7x^2–6x+1=x^4+(6x^3–2x^2)+(9x^2–6x+1)
= x^4+2x^2(3x–1)+(3x–1)^2 =(x^2+3x–1)^2
chỉnh lại tí
Đặt P(x)=x4+6x3+7x2- 6x+1
Đặt y=x2-1
=>y2=x4-2x2+1
P(x)=x4-2x2+1+6x3-6x+9x2
=(x2-1)2+6x(x2-1)+9x2
Q(y)=y2+6xy+9x2
=(y+3x)2
P(x)=(x2-1+3x)2
\(x^3+6x^2-13x-42\)
\(x^3+6x^2-13x-42\)
\(=\left(x+7\right)\left(x-3\right)\left(x+2\right)\)
b, \(2x^3-x^2+3x+6\)
\(=2x^3+2x^2-3x^2-3x+6x+6\)
\(=2x^2\left(x+1\right)-3x\left(x+1\right)+6\left(x+1\right)\)
\(=\left(x+1\right)\left(2x^2-3x+6\right)\)
\(\left(x^2+4x-3\right)^2-5x.\left(x^2+4x-3\right)+6x^2\)
\(=\left[\left(x^2+4x-3\right)^2-2.\left(x^2+4x-3\right).2,5x+\left(2,5x\right)^2\right]-\left(0,5x\right)^2\)
\(=\left(x^2+4x-3-2,5x\right)^2-\left(0,5x\right)^2\)
\(=\left(x^2+4x-3-2,5x-0,5x\right).\left(x^2-4x-3-2,5x+0,5x\right)\)
\(=\left(x^2+x-3\right).\left(x^2+2x-3\right)\)
Tham khảo nhé~
=[( x2)2 +2 x23y + (3y)2 ]-1 =(x2 +3y)2 -12 = (x2+3y-1)(x2+3y+1)
mk chỉnh đề
\(x^2-x-2=x^2-2x+x-2=x\left(x-2\right)+\left(x-2\right)=\left(x+1\right)\left(x-2\right)\)
\(x^2+6x+7=x^2+6x+9-2=\left(x+3\right)^2-2=\left(x+3-\sqrt{2}\right)\left(x+3+\sqrt{2}\right)\)
\(1;x^2-x-2\)
\(=x^2-2x+x-2\)
\(=x\left(x-2\right)+\left(x-2\right)\)
\(=\left(x+1\right)\left(x-2\right)\)
\(2,x^2+6x-7\)
\(=x^2-x+7x-7\)
\(=x\left(x-1\right)+7\left(x-1\right)=\left(x+7\right)\left(x-1\right)\)