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a) \(\left(x+3\right)^2-x\left(3x+1\right)^2+\left(2x+1\right)\left(4x^2-2x+1\right)-2x^2=54\)
=> x2 + 6x + 9 - x(9x2 + 6x + 1) + (2x)3 + 13 - 2x2 = 54
=> x2 + 6x + 9 - 9x3 - 6x2 - x + 8x3 + 1 - 2x2 = 54
=> (-9x3 + 8x3) + (x2 - 6x2 - 2x2) + (6x - x) + (9 + 1) = 54
=> -x3 - 7x2 + 5x + 10 = 54
=> -(x3 + 7x2 - 5x - 10) = 54
=> phương trình vô nghiệm
b) (x + 3)3 - (x - 3)(x2 + 3x + 9) + 6(x + 1)2 + 3x = -33
=> x3 + 9x2 + 27x + 27 - (x3 - 33) + 6(x2 + 2x + 1) + 3x = -33
=> x3 + 9x2 + 27x + 27 - x3 + 27 + 6x2 + 12x + 6 + 3x = -33
=> (x3 - x3) + (9x2 + 6x2) + (27x + 12x + 3x) + (27 + 27 + 6) = -33
=> 15x2 + 42x + 60 = -33
=> 15x2 + 42x + 60 + 33 = 0
=> 15x2 + 42x + 93 = 0
=> 3(5x2 + 14x + 31) = 0
=> 5x2 + 14x + 31 = 0
=> không tìm được x
a: \(\left(x+3\right)^3-x\left(2x+1\right)^2+\left(2x+1\right)\left(4x^2-2x+1\right)-3x^2=54\)
\(\Leftrightarrow x^3+9x^2+27x+27+8x^3+1-3x^2-x\left(2x+1\right)^2=54\)
\(\Leftrightarrow9x^3+6x^2+27x+28-4x^3-4x^2-x-54=0\)
\(\Leftrightarrow5x^3+2x^2+26x-26=0\)
\(\Leftrightarrow x\simeq0,835\)
b: \(\left(x-3\right)^3-\left(x-3\right)\left(x^2+3x+9\right)+6\left(x+1\right)^2+3x^2=33\)
\(\Leftrightarrow x^3-9x^2+27x-27-x^3+27+6x^2+12x+6+3x^2=33\)
\(\Leftrightarrow39x-21=33\)
=>39x=54
hay x=18/13
\(a.x\left(x-5\right)\left(x+5\right)-\left(x+2\right)\left(x^2-2x+4\right)=3\)
\(\Leftrightarrow x\left(x^2-5^2\right)-\left(x^3+2^3\right)=3\)
\(\Leftrightarrow x^3-25x-x^3-8=3\)
\(\Leftrightarrow x^3-x^3-25x=8+3\)
\(\Leftrightarrow x=\frac{11}{-25}\)
Vậy x có nghiệm là \(\frac{-11}{25}.\)
\(\)
a) = x3 + 9x2 + 27x + 27 - 9x3 -6x2 - x + 8x3 +1 -3x2 =54
26x +28 = 54
26x = 54-28 = 26
x = 1
b) = x3 - 9x2 + 27x -27 - x3 +27 +6x2 + 12x + 6 +3x2 = -33
39x +6 = -33
39x = -33-6 = -39
x = -1
Tìm x:
a/ \(\left(x+3\right)^3-x\left(3x-1\right)^2+\left(2x+1\right)\left(4x^2-2x+1\right)-3x^2=54\)
<=> \(x^3+9x^2+27x+27-9x^3+6x^2-x+8x^3+1-3x^2-54=0\)<=> \(12x^2+26x-26=0\)
<=> \(\left[\begin{array}{} x=\dfrac{-13+\sqrt{481}}{12}\\ x=\dfrac{-13-\sqrt{481}}{12} \end{array} \right.\)
b/ \(\left(x-3\right)^3-\left(x-3\right)\left(x^2+3x+9\right)+6\left(x+1\right)^2+3x^2=-33\)
<=> \(x^3-9x^2+27x-27-x^3+27+6x^2+12x+6+3x^2+33=0\)
<=> 39x+39=0
<=> x=-1
1.
(x + 3)3 - x(3x + 1)2 + (2x + 1)(4x2 - 2x + 1) - 3x2 = 54
x3 + 9x2 + 27x + 27 - x(9x2 + 6x + 1) + 8x3 + 1 - 3x2 = 54
9x3 + 6x2 + 27x - 9x3 - 6x2 - x
= 54 - 27 - 1
26x = 26
x = 1