Moi nguoi giup minh vs:
Rut gon bieu thuc:
a, 5^n +5^(n+2)
b,2/3. 3^(n-1)
Những câu hỏi liên quan
cho 2 bieu thuc:
A=(\(\sqrt{20}\) -\(\sqrt{45}\) +3\(\sqrt{5}\) ).\(\sqrt{5}\) va B=\(\dfrac{x+1-2\sqrt{x}}{\sqrt{x}-1}\) +\(\dfrac{x+\sqrt{x}}{\sqrt{x}+1}\) (Dieu kien: x>0, x khac 1
a) Rut gon bieu thuc A va B
b)Tim cac gia tri cua x de gia tri cua bieu thuc A bang 2lan gia tri B
a: \(A=\left(2\sqrt{5}-3\sqrt{5}+3\sqrt{5}\right)\cdot\sqrt{5}=2\sqrt{5}\cdot\sqrt{5}=10\)
\(B=\dfrac{\left(\sqrt{x}-1\right)^2}{\sqrt{x}-1}+\dfrac{\sqrt{x}\left(\sqrt{x}+1\right)}{\sqrt{x}+1}\)
\(=\sqrt{x}-1+\sqrt{x}=2\sqrt{x}-1\)
b: A=2B
=>\(10=4\sqrt{x}-2\)
=>\(4\sqrt{x}=12\)
=>x=9(nhận)
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Rut gon bieu thuc :
D = 57 + 511 + 515 + ... + 54k+3
(K\(∈\)N , K > 2)
Nhanh nha moi nguoi 2 nhanh nhat minh tick cho con ai la giao vien tra loi gium em a !
\(D=5^7+5^{11}+5^{15}+...+5^{4k+3}\) (1)
Nhân D với 54 ta được:
\(5^4.D=5^{11}+5^{15}+...+5^{4k+7}\) (2)
Lấy (2) trừ đi (1) ta được:
\(5^4.D-D=5^{4k+7}-5^7\)
=> \(D=\frac{5^7\left(5^{4k}-1\right)}{5^4-1}\)
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Rut gon bieu thuc :
D = 57 + 511 + 515 + ... + 54k+3
(K\(\in\)N , K > 2)
Nhanh nha moi nguoi 2 nhanh nhat minh tick cho con ai la giao vien tra loi gium em a !
cac ban oi giup minh cau nay vs
rut gon cac bieu thuc sau
3x^2 - 2x . (5+1,5x) + 10
giai giup mik vs
\(3x^2-2x.\left(5+1,5x\right)+10\)
\(=3x^2-2x.5-2x.1,5x+10\)
\(=3x^2-3x^2-10x+10\)
\(=10-10x\)
\(=10.\left(1-x\right)\)
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rut gon bieu thuc -3/5<x<1/7
B=|-x+1/7|+|-x-3/5|-2/6
help me! giup mk voi minh can gap do
rut gon bieu thuc
1/(1^4+1^2+1)+2/(2^4+2^2+1)+3/(3^4+3^2+1)+...+2014/(2014^4+2014^2+2014)=...
{giup minh vs}
2x+2/(x+1)(x-1) rut gon
mong moi nguoi giup do
\(\frac{2x+2}{\left(x+1\right)\left(x-1\right)}.ĐKXĐ:x\ne\pm1\)
\(=\frac{2\left(x+1\right)}{\left(x+1\right)\left(x-1\right)}=\frac{2}{x-1}\)
~~
Rut gon bieu thuc: A=1+ 1/2+ 1/22+ 1/23+ ... +1/22012
GIUP MINH NHANH NHE
2A = 2 + 1 + 1/2 + 1/2^2 + ... + 1/2^2011
A = 1 + 1/2 + .. + 1/2^2011 + 1/2^2012
2A - A = 2 + 1 + 1/2 + .. + 1/2^2011 - 1 - 1/2 - ... - 1/2^2011 - 1/2^2012
A = 2 - 1/2^2012
A = \(\frac{2^{2012}-2}{2^{2012}}\)
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A = 1+1/2+1/2^2+1/2^3+.....+1/2^2012
2A= 2. (1+1/2+1/2^2+1/2^3+.....+1/2^2012)
2A= 2 + 1 + 1/2 + 1/2^2 + 1/2^3 + ...+ 1/2^2011
2A - A= (2 + 1 + 1/2 + 1/2^2 + 1/2^3+ ...+ 1/2^2011) - (1+1/2+1/2^2+1/2^3+.....+1/2^2012)
1A= 2 + 1 + 1/2 + 1/2^2 + 1/2^3 + ...+ 1/2^2011 - 1-1/2-1/2^2+1/2^3+.....+1/2^2012
1A= 2 - 1/2^2012
A= 2-1/2^2012
A= 2 - 1/2^2012
Bai1:
a- 3x^2 - 7x +2 b- a(x^2 +1 ) - x (a^2 +1)
Bai2 : Cho bieu thuc
A= (2+x/ 2-x - 4x^2 / x^2 -4 - 2-x/ 2+x ) : x^2 - 3x / 2x^2 - x ^3
a- Tim DKXD roi rut gon bieu thuc A ?
b- Tim gia tri cua x de A>0?
c- Tinh gia tri cua A TRong truong hop : \vbar x-7 \vbar=4
Giup mk nha moi nguoi !!!!!!!!!
Bài 2:
a: ĐKXĐ: \(x\notin\left\{0;2;-2;3\right\}\)\(A=\left(\dfrac{-\left(x+2\right)}{x-2}-\dfrac{4x^2}{\left(x-2\right)\left(x+2\right)}+\dfrac{x-2}{x+2}\right):\dfrac{x\left(x-3\right)}{x^2\left(2-x\right)}\)
\(=\dfrac{-x^2-4x-4-4x^2+x^2-4x+4}{\left(x-2\right)\left(x+2\right)}\cdot\dfrac{-x\left(x-2\right)}{x-3}\)
\(=\dfrac{-4x^2-8x}{\left(x+2\right)}\cdot\dfrac{-x}{x-3}\)
\(=\dfrac{-4x\left(x+2\right)}{x+2}\cdot\dfrac{-x}{x-3}=\dfrac{4x^2}{x-3}\)
b: Để A>0 thì x-3>0
hay x>3
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