(6x^{2}y+8y^{3}-3x)+ A = 4x^{2}y-11x(6x2y+8y3−3x)+A=4x2y−11x
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a) \(x^5+4x+5=\left(x^5+x^4\right)-\left(x^4+x^3\right)+\left(x^3+x^2\right)-\left(x^2+x\right)+\left(5x+5\right)=x^4\left(x+1\right)-x^3\left(x+1\right)+x^2\left(x+1\right)-x\left(x+1\right)+5\left(x+1\right)=\left(x^4-x^3+x^2-x+5\right)\left(x+1\right)\)
b) \(x^4+6x^3+11x^2+6x+1=\left(x^4+3x^3+x^2\right)+\left(3x^3+9x^2+3x\right)+\left(x^2+3x+1\right)=x^2\left(x^2+3x+1\right)+3x\left(x^2+3x+1\right)+\left(x^2+3x+1\right)=\left(x^2+3x+1\right)^2\)
c) \(64x^4+1=\left[\left(8x^2\right)^2+16x^2+1\right]-16x^2=\left(8x^2+1\right)^2-\left(4x\right)^2=\left(8x^2-4x+1\right)\left(8x^2+4x+1\right)\)d) \(81x^4+4=\left[\left(9x^2\right)^2+36x^2+2^2\right]-36x^2=\left(9x^2+2\right)^2-\left(6x\right)^2=\left(9x^2-6x+2\right)\left(9x^2+6x+2\right)\)
c, x4+6x3+11x2+6x+1
=x4+6x3+9x2+2x2+6x+1
=x4+9x2+1+6x3+2x2+6x
=(x2)2+(3x)2+12+2.x2.3x+2.x2.1+2.3x.1 (1)
Áp dụng hằng đẳng thức (a+b+c)2=a2+b2+c2+2ab+2ac+2bc
=> (1)=(x2+3x+1)2
Câu a nhé bạn:
a, 3x2−22xy−4x+8y+7y2+1
=3x2-21xy-xy-3x-x+7y+y+7y2+1
=(3x2−21xy−3x)−(xy-7y2-y)−(x-7y-1)
=3x(x−7y−1)−y(x−7y−1)−(x−7y−1)
=(3x−y−1)(x−7y−1)
b.\(x^3+6x^2+11x+6=0\)
\(\Leftrightarrow x^3+x^2+5x^2+5x+6x+6=0\)
\(\Leftrightarrow x^2\left(x+1\right)+5x\left(x+1\right)+6\left(x+1\right)=0\)
\(\Leftrightarrow\left(x+1\right)\left(x^2+5x+6\right)=0\)
\(\Leftrightarrow\left(x+1\right)\left(x^2+2x+3x+6\right)=0\)
\(\Leftrightarrow\left(x+1\right)\left(x+2\right)\left(x+3\right)=0\)
\(\Leftrightarrow\)\(x+1=0\)hoặc \(x+2=0\)hoặc \(x+3=0\)
\(\Leftrightarrow\)...... tự viết nha bn
a) (6x5 - 3x2):3x - (4x2 + 8x):4x = 5
\(\Rightarrow\)2x4 - x - x - 2 = 5
\(\Rightarrow\)2(x4 - x -1) = 5
\(\Rightarrow\)x4 - 2x2 + 1 + 2x2 - 2 = 2.5
\(\Rightarrow\)(x2 - 1)2 + 2(x2 - 1) + 1 - \(\frac{7}{2}\) = 0
\(\Rightarrow\)x4 = \(\frac{7}{2}\)
\(\Rightarrow\)x = \(\pm\)\(\sqrt[4]{\frac{7}{2}}\)
b) x3 + 6x2 + 11x +6 = 0
\(\Rightarrow\)x3 + 6x2 + 12x + 8 - x - 2 = 0
\(\Rightarrow\)(x + 2)3 - (x + 2) = 0
\(\Rightarrow\)(x + 2)(x-1)(x+3)=0
\(\Rightarrow\)x + 2 = 0 \(\Rightarrow\)x = -2
x - 1 =0 \(\Rightarrow\)x = 1
x + 3 = 0 \(\Rightarrow\)x = -3
Vay.....
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