Cho biểu thức \(P=\left(x-4\right)^{\left(x-5\right)^{\left(x-6\right)^{\left(x+6\right)^{\left(x+5\right)}}}}\).Hãy tính giá trị của P với x=7 ?
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thay x = 7 vào biểu thức, ta đc:
\(P=\left(7-4\right)^{\left(7-5\right)^{\left(7-6\right)^{\left(7+6\right)^{\left(7+5\right)}}}}=3^{2^{1^{13^{12}}}}\)
\(=3^{2^1}=9\)
\(\left(x-6\right)^{\left(x+6\right)^{\left(x+5\right)}}=\left(7-6\right)^{\left(7+6\right)^{\left(7+5\right)}}=1^{13^{12}}=1\)
=> P(1) = \(\left(7-4\right)^{\left(7-5\right)^1}=3^2=9\)
Ta có x-6=7-6=1
=>A=(x-4)(x-5)=(7-4)(7-5)=32=9
Vậy giá trị của A tại x=7 là 9
Thay x = 7 vào p, ta đc:
\(p=\left(7-4\right)^{\left(7-5\right)^{\left(7-6\right)^{\left(7+6\right)^{7+5}}}}\)
\(=3^{2^{1^{13^{12}}}}=9\)
Vì | x-1| ; |x+2|; |x-3| ; |x+4| ; |x-5|; |x+6| ; |x-7| ; |x+8| ; |x-9| luôn luôn < hoặc = 0
vì vậy min của T =0
\(T=|x-1|+|x+2|+|x-3|+|x+4|+|x-5|+|x+6|+|x-7|+|x+8|+|x-9|\)
\(\Rightarrow T=|x-1|+|x+2|+|3-x|+|x+4|+|5-x|+|x+6|+|7-x|+|x+8|+|9-x|\)
\(\Rightarrow T\ge|x-1+x+2+3-x+x+4+5-x+x+6+7-x+x+8+9-x|\)
\(\Rightarrow T\ge|43|\)
\(\Rightarrow T\ge43\)
Vậy \(Min_T=43\)
Bài 2:
\(B=\left(1-\frac{1}{2}\right).\left(1-\frac{1}{3}\right).\left(1-\frac{1}{4}\right).......\left(1-\frac{1}{2004}\right)\)
\(=\frac{1}{2}.\frac{2}{3}.\frac{3}{4}....\frac{2003}{2004}\)
\(=\frac{1}{2004}\)
đk : \(x\ge0,x\ne1\)
\(=>P=\left[\dfrac{2\left(\sqrt{x}+2\right)-5}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+2\right)}\right]:\left[\dfrac{x+\sqrt{x}-2+3-x}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+2\right)}\right]\)
\(P=\left[\dfrac{2\sqrt{x}-1}{\left(\sqrt{x}-1\right)\left(\sqrt{x}+2\right)}\right].\left[\dfrac{\left(\sqrt{x}-1\right)\left(\sqrt{x}+2\right)}{\sqrt{x}+1}\right]\)
\(P=\dfrac{2\sqrt{x}-1}{\sqrt{x}+1}\)
b,\(x=6-2\sqrt{5}=\left(\sqrt{5}-1\right)^2\) thay vào P
\(=>P=\dfrac{2\sqrt{\left(\sqrt{5}-1\right)^2}-1}{\sqrt{\left(\sqrt{5}-1\right)^2}+1}=\dfrac{2\sqrt{5}-3}{\sqrt{5}}\)
c,\(=>\dfrac{2\sqrt{x}-1}{\sqrt{x}+1}=\dfrac{1}{\sqrt{x}}=>2x-\sqrt{x}=\sqrt{x}+1\)
\(=>2x-2\sqrt{x}-1=0< =>2\left(x-\sqrt{x}-\dfrac{1}{2}\right)=0\)
\(=>x-\sqrt{x}-\dfrac{1}{2}=>\Delta=1-4\left(-\dfrac{1}{2}\right)=3>0=>\left[{}\begin{matrix}x1=\dfrac{1+\sqrt{3}}{2}\\x2=\dfrac{1-\sqrt{3}}{2}\end{matrix}\right.\)
đối chiếu đk loại x2 còn x1 thỏa
Chắc là \(q\left(x\right)=x^2-4????\)
\(f\left(2\right)=2^5+2^2+1=37\) ; \(f\left(-2\right)=-27\)
Do \(f\left(x\right)\) có 5 nghiệm nên f(x) có dạng:
\(f\left(x\right)=\left(x-x_1\right)\left(x-x_2\right)\left(x-x_3\right)\left(x-x_4\right)\left(x-x_5\right)\)
\(\Rightarrow f\left(2\right)=\left(2-x_1\right)\left(2-x_2\right)\left(2-x_3\right)\left(2-x_4\right)\left(2-x_5\right)=37\)
\(f\left(-2\right)=\left(-2-x_1\right)\left(-2-x_2\right)\left(-2-x_3\right)\left(-2-x_4\right)\left(-2-x_5\right)=-27\)
\(\Rightarrow\left(2+x_1\right)\left(2+x_2\right)\left(2+x_3\right)\left(2+x_4\right)\left(2+x_5\right)=27\)
\(A=\left(x_1^2-4\right)\left(x^2_2-4\right)\left(x_3^2-4\right)\left(x_4^2-4\right)\left(x^2_5-4\right)\)
\(A=-\left(2-x_1\right)\left(2-x_2\right)\left(2-x_3\right)\left(2-x_4\right)\left(2-x_5\right)\left(2+x_1\right)\left(2+x_2\right)\left(2+x_3\right)\left(2+x_4\right)\left(2+x_5\right)\)
\(A=-37.27=-999\)
\(\frac{x\left(x+5\right)+y\left(y+5\right)+2\left(xy-3\right)}{x\left(x+6\right)+y\left(y+6\right)2xy}\)
=\(\frac{x^2+5x+y^2+5y+2xy-3}{x^2+6x+y^2+6y+2xy}\)
triệt tiêu x2;y2;2xy ta được:
\(\frac{5x+5y-3}{6x+6y}=\frac{5\left(x+y\right)-3}{6\left(x+y\right)}\)
=\(\frac{5.2010-3}{6.2010}=\frac{3349}{4020}\)
x = 7 => x - 6 = 1
=> \(\left(x-6\right)^{\left(x+6\right)^{\left(x+5\right)}}=1^{\left(x+6\right)^{\left(x+5\right)}}=1\)
\(\Rightarrow P=\left(x-4\right)^{\left(x-5\right)^1}=\left(7-4\right)^{\left(7-5\right)}=3^2=9\)