Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
1. Tìm x
a) 1+2+3+...+x = 210
=> \(\frac{x\left(x+1\right)}{2}=210\)
=> x = 20
b) \(32.3^x=9.3^{10}+5.27^3\)
=>\(32.3^x=9.3^{10}+5.3^9\)(\(27^3=\left(3^3\right)^3=3^9\))
=>\(32.3^x=9.3.3^9+5.3^9\)
=>\(32.3^x=3^9\left(9.3+5\right)\)
=>\(32.3^x=3^9.32\)
=>x = 9
2.
Ta có 2A = 3A - A
=> 2A = \(3\left(1+3+3^2+3^3+....+3^{10}\right)\)\(-\)\(1-3-3^2-3^3-....-3^{10}\)
=> 2A = \(3+3^2+3^3+.....+3^{11}-\)\(1-3-3^2-3^3-...-3^{10}\)
=> 2A = \(3^{11}-1\)
=> 2A+1 = \(3^{11}-1+1\)=\(3^{11}\)
=> n = 11
Ta có : a)1 + 2 + 3 + ... + x = 210
=> \(\frac{x\left(x+1\right)}{2}=210\)
=> x(x + 1) = 420
=> x(x + 1) = 20.21
=> x = 20
a, \(\frac{3}{4}x-\frac{1}{5}=\frac{7}{4}x+\frac{11}{5}\)
\(\Rightarrow\frac{3}{4}x-\frac{7}{4}x=\frac{11}{5}+\frac{1}{5}\)
\(\Rightarrow-x=\frac{12}{5}\Rightarrow x=-\frac{12}{5}\)
Vậy ...
b, \(\frac{x+1}{2}=\frac{8}{x+1}\)
\(\Rightarrow\left(x+1\right)^2=16\)
\(\Rightarrow x+1=4\)hoặc \(x+1=-4\)
\(\Rightarrow x=3\) hoặc \(x=-5\)
Vậy ..
3/4x-7/4x=1/5+11/5
(3/4-7/4).x=12/5
-1.x=12/5
x=12/5:-1
x=-12/5
vậy x=-12/5
b;\(\frac{x}{17}=\frac{60}{204}\)
=> \(x=60.17:204=5\)
c; \(6+\frac{x}{33}=\frac{7}{11}\)
=> \(6=\frac{7}{11}-\frac{x}{33}\)
=> \(6=\frac{21}{33}-\frac{x}{33}\)
=> \(6=\frac{21-x}{33}\)
=> \(21-x=198\)
=> \(x=21-198\)
=> \(x=-117\)
a, x=27-126
x=-99
b,\(317-\left(4x+11\right):3=20\\ 317-\left(4x+11\right)=20.3\\ 317-\left(4x+11\right)=60\\ 4x+11=317-60\\ 4x+11=257\\ 4x=257-11\\ 4x=246\\ x=61,5\)