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\(\left(-3x-2\right)^2+\left(3x+5\right)\left(5-3x\right)=-7\)
\(\Leftrightarrow9x^2+12x+4+15x-9x^2+25-15x=-7\)
\(\Leftrightarrow12x+36=0\Leftrightarrow x=-3\)
\(\left(x+2\right)\left(x^2+2x+2\right)-x\left(x-8\right)^2=\left(4x-3\right)\left(4x+3\right)\)
\(\Leftrightarrow x^3+2x^2+2x+2x^2+4x+4-x\left(x^2-16x+64\right)=16x^2-9\)
\(\Leftrightarrow x^3+4x^2+6x+4-x^3+16x^2-64=16x^2-9\)
\(\Leftrightarrow4x^2+6x-51=0\)
\(\cdot\Delta=6^2-4.4.\left(-51\right)=852\)
Vậy pt có 2 nghiệm phân biệt
\(x_1=\frac{-6+\sqrt{852}}{8}\);\(x_2=\frac{-6-\sqrt{852}}{8}\)
a: \(\Leftrightarrow5x\left(x^2-6x+9\right)-5\left(x^3-3x^2+3x-1\right)+15x^2-60-5=0\)
\(\Leftrightarrow5x^3-30x^2+45x-5x^3+15x^2-15x+5+15x^2-65=0\)
\(\Leftrightarrow30x-60=0\)
hay x=2
b: \(\Leftrightarrow x^3+9x^2+27x+27-x\left(9x^2+6x+1\right)+8x^3+1-3x^2=42\)
\(\Leftrightarrow9x^3+6x^2+27x+28-9x^3-6x^2-x=42\)
=>26x=14
hay x=7/13
a)(2x-3)2=(x+5)2
=>4x2-12x+9=x2+10x+25
=>3x2-22x-16=0
=>3x2+2x-24x-16=0
=>x(3x+2)-8(3x+2)=0
=>(x-8)(3x+2)=0
=>x=8 hoặc x=-2/3
b)X2.(x-1)-4x2+8x-4=0
=>x2(x-1)-4x2+4x+4x-4=0
=>x2(x-1)-4x(x-1)-4(x-1)=0
=>x2(x-1)-(4x-4)(x-1)=0
=>(x2-4x+4)(x-1)=0
=>(x-2)2(x-1)=0
=>x=2 hoặc x=1
c) 4x2- 25 - (2x- 5) . ( 2x+7)=0
=>4x2-25-(4x2+14x-10x-35)=0
=>4x2-25-4x2-14x+10x+35=0
=>-4x+10=0
=>-4x=-10 <=>x=5/2
d) x3+27+(x+3).(x-9)=0
=>x3+33+(x+3)(x-9)=0
=>(x+3)(x2-3x+9)+(x+3)(x-9)=0
=>(x2-3x+9+x-9)(x+3)=0
=>(x2-2x)(x+3)=0
=>x(x-2)(x+3)=0
=>x=0 hoặc x=2 hoặc x=-3
e) (x-2).(x+5)- x2+4=0
=>(x-2)(x+5)-(x-2)(x+2)=0
=>(x-2)(x+5-x-2)=0
=>3(x-2)=0 <=>x=2
Sau khi khai triển hằng đẳng thức và thực hiện chuyển vế bạn sẽ đk kết quả như này!(\(\left(2x-3\right)^2=\left(x+5\right)^2=3x^2-22x-14\)
Câu a :
\(\left(x+2\right)\left(x^2-2x+4\right)-x\left(x^2+2\right)=15\)
\(\Leftrightarrow x^3+8-x^3-2x=15\)
\(\Leftrightarrow-2x=7\)
\(\Leftrightarrow x=-\dfrac{7}{2}\)
Câu b :
\(\left(x+3\right)^3-x\left(3x+1\right)^2+\left(2x+1\right)\left(4x^2-2x+1\right)=28\)
\(\Leftrightarrow x^3+9x^2+27x+27-9x^3-6x^2-x+8x^3+1=28\)
\(\Leftrightarrow3x^2+26x=0\)
\(\Leftrightarrow x\left(3x+26\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\3x+26=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{26}{3}\end{matrix}\right.\)
a) \(\left(x+2\right)\left(x^2-2x+4\right)-x\left(x^2+2\right)=15\)
\(\rightarrow x^3-2x^2+4x+2x^2-4x^2+8-x^3-2x=15\)
\(\rightarrow2x+8=15\)
\(\rightarrow2x=15-8=7\)
\(\Rightarrow x=7:2=3,5\)
Do ko có t/gian nên ko kịp lm câu b
Bài 1:
a: \(A=3\left(x^2-2x+1\right)-\left(x^2+2x+1\right)+2\left(x^2-9\right)-\left(4x^2+12x+9\right)-5+20x\)
\(=3x^2-6x+3-x^2-2x-1+2x^2-18-\left(4x^2+12x+9\right)-5+20x\)
\(=4x^2-8x-16-5+20x-4x^2-12x-9\)
\(=-30\)
b: \(B=5x\left(x^2-49\right)-x\left(4x^2-4x+1\right)-\left(x^3+4x^2-246x\right)-175\)
\(=5x^3-245x-4x^3+4x^2-x-x^3-4x^2+246x-175\)
\(=-175\)
d: \(D=25x^2-20x+4-36x^2-12x-1+11\left(x^2-4\right)-48+32x\)
\(=-11x^2-32x+3-48+32x+11x^2-44\)
=-89
x( x + 2 )2 - ( x - 1 )3
= x( x2 + 4x + 4 ) - ( x3 - 3x2 + 3x - 1 )
= x3 + 4x2 + 4x - x3 + 3x2 - 3x + 1
= 7x2 + x + 1
4x( x + 5 ) + ( 3 - 2x )( 2x + 3 )
= 4x2 + 20x + 9 - 4x2
= 20x + 9
( x - 3 )3 - ( x + 3 )3
= x3 - 9x2 + 27x - 27 - ( x3 + 9x2 + 27x + 27 )
= x3 - 9x2 + 27x - 27 - x3 - 9x2 - 27x - 27
= -18x2 - 54
x( 2x - 7 ) - 2( x + 3 )2
= 2x2 - 7x - 2( x2 + 6x + 9 )
= 2x2 - 7x - 2x2 - 12x - 18
= -19x - 18
\(x\left(x+2\right)^2-\left(x-1\right)^3\)
\(=x\left(x^2+4x+4\right)-\left(x^3-3x^2+3x-1\right)\)
\(=x^3+4x^2+4x-x^3+3x^2-3x+1\)
\(=7x^2+x+1\)