M = x3+ 18x2+ 108x + 16 tại x = - 26. giải bằng hẳng đẳng thức giúp e ạa
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c)
\(x^3-3.x^2.6+3.x.6^2-6^3=0\)
\(\left(x-6\right)^3=0\)
x-6=0
x=6
d)
\(x^3-3.x^2.1+3.x.1^2-1-x^3-3x-2=0\)
\(x^3-3x^2+3x-1-x^3-3x^2-2=0\)
\(-6x^2-3=0\)
\(-3\left(2x^2+1\right)=0\)
\(2x^2+1=0\)
2x2=-1
x2=1/2
x=\(\dfrac{\sqrt{2}}{2}\)
a) (x+4)(x2 - 4x + 16 ) - x(x-5) = 264
x3 + 43 - x(x2 - 25) = 264
x3 + 64 - x3 + 25x= 264
64 + 25x = 264
25x = 264-64
25x= 200
x = \(\dfrac{200}{25}\) = 8
b) (x-2)3 - (x-2)(x2 + 2x + 4 ) + 6(x-2)(x+2) = 60
x3 - 6x2 + 12x - 8 - ( x3 - 23 ) + 6(x2 - 4 ) = 60
x3 - 6x2 + 12x - 8 - x3 + 8 + 6x2 -24 = 60
12x - 24 = 60
12x = 60 + 24
12x = 84
x = \(\dfrac{84}{12}\) = 7
Lời giải:
A) Tại $x=35$ thì \(x-35=0\)
\(A=x^3-15x^2+75x=x^3-35x^2+20x^2+75x\)
\(=x^3-35x^2+20x^2-700x+775x\)
\(=x^2(x-35)+20x(x-35)+775x\)
\(=775x=775.35=27125\)
B) \(x=-26\rightarrow x+26=0\)
\(B=x^3+18x^2+108x+16\)
\(=x^3+26x^2-8x^2-208x+316x+16\)
\(=x^2(x+26)-8x(x+26)+316x+16\)
\(=316x+16=316.-26+16=-8200\)
C)
\(C=(x^2-4y^2)(x^2-2xy+4y^2)(x^2+2xy+4y^2)\)
\(=(x-2y)(x+2y)(x^2-2xy+4y^2)(x^2+2xy+4y^2)\)
\(=[(x-2y)(x^2+2xy+4y^2)][(x+2y)(x^2-2xy+4y^2)]\)
\(=[x^3-(2y)^3][x^3+(2y)^3]\)
\(=(-8-1)(-8+1)=63\)
a) \(=\left(x-2\right)^2\)
b) \(=\left(2x+1\right)^2\)
c) \(=\left(4x-3y\right)\left(4x+3y\right)\)
d) \(=\left(4-x-3\right)\left(4+x+3\right)=\left(1-x\right)\left(x+7\right)\)
e) \(=\left(2x-3x+1\right)\left(2x+3x-1\right)=\left(1-x\right)\left(5x-1\right)\)
f) \(=\left(x-y\right)\left(x^2+xy+y^2\right)\)
g) \(=\left(x+3\right)\left(x^2-3x+9\right)\)
h) \(=\left(x+2\right)^3\)
i) \(=\left(1-x\right)^3\)
a: \(x^2-4x+4=\left(x-2\right)^2\)
b: \(4x^2+4x+1=\left(2x+1\right)^2\)
g: \(x^3+27=\left(x+3\right)\left(x^2-3x+9\right)\)
a) \(=x^2-\left(2y\right)^2=\left(x-2y\right)\left(x+2y\right)\)
b) \(=x^2-\left(3y\right)^2=\left(x-3y\right)\left(x+3y\right)\)
c) \(=\left(2x-1\right)^2-\left(2y\right)^2=\left(2x-1-2y\right)\left(2x-1+2y\right)\)
d) \(=x^2-10xy+\left(5y\right)^2=\left(x-5y\right)^2\)
e) \(=\left(3x\right)^2-6x+1=\left(3x-1\right)^2\)
f) \(=\left(5x\right)^2+20x+4=\left(5x+2\right)^2\)
\(M=x^3+18x^2+108x+16\)
\(M=x^3+18x^2+108x+216-200\)
\(M=\left(x+6\right)^3-200\)
\(M=\left(-20\right)^3-200\)
\(M=-8000-200\)
\(M=-8200\)