a: \(\Leftrightarrow\left(-2\right)^n=\dfrac{128}{2}=64\)
hay n=6
b: \(\Leftrightarrow3^x\cdot\dfrac{7}{3}=7\cdot3^4\)
\(\Leftrightarrow3^x=3^5\)
hay x=5
B = 1+ \(\dfrac{1}{2}\left(1+2\right)+\dfrac{1}{3}\left(1+2+3\right)+\dfrac{1}{4}\left(1+2+3+4\right)+.......+\dfrac{1}{x}\left(1+2+3+4+....+x\right)\)
Tìm số nguyên dương x để B = 115
ĐỀ 1:
1. Tính:
a. \(\dfrac{7}{23}\left[\left(\dfrac{-8}{6}\right)-\dfrac{45}{18}\right]\)
b. \(\dfrac{1}{5}:\dfrac{1}{10}-\dfrac{1}{3}\left(\dfrac{6}{5}-\dfrac{9}{4}\right)\)
c. \(\dfrac{3}{5}.\left(\dfrac{-8}{3}\right)-\dfrac{3}{5}:\left(-6\right)\)
d. \(\dfrac{1}{2}\left(\dfrac{4}{3}+\dfrac{2}{5}\right)-\dfrac{3}{4}\left(\dfrac{8}{9}+\dfrac{16}{3}\right)\)
e. \(\dfrac{6}{7}:\left(\dfrac{3}{26}-\dfrac{3}{13}\right)+\dfrac{6}{7}\left(\dfrac{1}{10}-\dfrac{8}{5}\right)\)
2. Tìm x, biết:
a. \(1\dfrac{2}{5}x+\dfrac{3}{7}=\dfrac{4}{5}\)
b. |x - 1,5| = 2
c. \(\dfrac{4}{5}-\left|x-\dfrac{1}{6}\right|=\dfrac{2}{3}\)
d. 3x . 2x = 216
e. \(\dfrac{1}{2}\left(x-\dfrac{1}{3}\right)+\dfrac{-1}{2}=\dfrac{3}{4}\)
* Lm nhanh nha
Ths you <3
ĐỀ 2:
1. Tính:
A. \(\left(-\dfrac{2}{3}\right)^2+\left(-\dfrac{7}{8}\right)+\left(-\dfrac{11}{12}\right)\)
B. \(\left(\dfrac{-1}{3}\right)^2:\dfrac{1}{6}-2.\left(\dfrac{-1}{2}\right)^3\)\
C. \(\dfrac{-1}{5}-\left(\dfrac{1}{2}+\dfrac{3}{4}\right)^2:\dfrac{5}{8}\)
D. \(\left|\dfrac{-3}{2}+1,2\right|+1\dfrac{2}{3}:6\)
2. Tìm x, biết:
a. \(\dfrac{2}{3}x-\dfrac{1}{3}x=\dfrac{5}{12}\)
b. \(\left(x-\dfrac{12}{7}\right):1\dfrac{1}{5}=\dfrac{4}{7}\)
c. \(\dfrac{2}{5}+\left|x+1\right|=\dfrac{3}{4}\)
3. Tìm x, y biết:
a. \(\dfrac{x}{18}=\dfrac{y}{15}\)và x - y = -30
b. 7x = 9x và 10x - 8x = 68
c. \(\left(x-\dfrac{1}{2}\right)^{50}+\left(y+\dfrac{1}{3}\right)^{40}=0\)
* Lm nhanh nha
Tìm số nguyên x biết:
a. \(-4\dfrac{3}{5}.2\dfrac{4}{23}\)<x<\(-2\dfrac{3}{5}:1\dfrac{6}{15}\) b. \(-4\dfrac{1}{3}.\left(\dfrac{1}{2}-\dfrac{1}{6}\right)< x< -\dfrac{2}{3}\left(\dfrac{1}{3}-\dfrac{1}{2}-\dfrac{3}{4}\right)\)
1) Tìm số tự nhiên x,y biết :
a) \(0,25^x.12^x=243\)
b) \(38^y:19^y\) = 512
2) Tìm x :
a) \(3^x+3^{x+2}=2430\)
b) \(2^{x+3}-2^x=224\)
3) Tìm số hữu tỉ x :
a) \(\left(x-\dfrac{1}{4}\right)^2=\dfrac{4}{9}\)
b)\(\left(x+0,7\right)^3=-27\)
4) Tìm x:
a)\(\left(\dfrac{2}{5}-3x\right)^2=\dfrac{9}{25}\)
b) \(\left(\dfrac{2}{3}x-\dfrac{1}{3}\right)^5=\dfrac{1}{243}\)
Rút gọn:
\(A=\left[\left(\dfrac{3}{1+x}-\dfrac{x}{x^2+x+1}\right):\dfrac{2x^2+3x}{x+1}+\dfrac{3}{x+1}\right]\cdot\dfrac{x^2+x}{1+3x}\)
\(B=\left[\dfrac{a}{2a-6}-\dfrac{a^2}{a^2-9}+\dfrac{a}{2a-9}\cdot\left(\dfrac{3}{a}+\dfrac{1}{3-a}\right)\right]:\dfrac{a^2-5a-6}{18-2a^2}\)
Tìm các số hữu tỷ x,biết rằng:
a,\(\left(x-\dfrac{5}{3}\right):-1\dfrac{3}{4}=0\)
b,\(\left(x-\dfrac{1}{5}\right)\left(1\dfrac{3}{5}+2x\right)=0\)
c,\(\left(x-\dfrac{4}{7}\right):\left(x+\dfrac{1}{2}\right)>0\)
d,(2x-3):\(\left(x+1\dfrac{3}{4}\right)< 0\)
Phương trình : \(\dfrac{1}{\left(x-1\right)\left(x-2\right)}+\dfrac{1}{\left(x-2\right)\left(x-3\right)}=\dfrac{1}{\left(x-3\right)\left(x-4\right)}+\dfrac{1}{\left(x-1\right)\left(x-4\right)}\)
1) Tìm GTNN:
a) B = \(\left|x-2017\right|+\left|x-20\right|\)
b) C = \(\left|x-3\right|+\left|x-5\right|\)
c) C = \(\left|x^2+4\right|+3\)
d) D = \(\sqrt{x^2+1}-2\)
2) Tìm x:
a) \(\left(x+\dfrac{4}{5}\right)^2=\dfrac{9}{25}\)
b) \(\left|x-\dfrac{3}{7}\right|=-2\)
c) \(\sqrt{x+7}-2=4\)
d) \(x^2-\dfrac{7}{9}x=0\)
e) \(\dfrac{x+1}{2009}+\dfrac{x+5}{2005}+\dfrac{x+6}{2004}+\dfrac{x+10}{2010}=-4\)
3) Tìm a,b,c \(\in\) Q, biết:
ab = 2; bc = 3; ca = 54
4) Cho A = \(1-5+9-13+17-21+25-....\) n số hạng
a) Tính A theo n
b) Viết số hạng thứ n của A theo n
5) \(S_n=1-2+3-4+...+\left(-1\right)^{n-1}.n\)
Với n = 1,2,3,....
Tính \(S_{35}+S_{60}\)
6) So sánh
a) \(\left(\dfrac{-1}{16}\right)^{100}\) và \(\left(\dfrac{-1}{2}\right)^{500}\)
b) \(\left(-32\right)^9\) và \(\left(-18\right)^{13}\)
7) Sắp xếp từ nhỏ đến lớn:
a = \(2^{100}\) ; b = \(3^{75}\); c = \(5^{50}\)
