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KN
12 tháng 7 2019
Áp dụng t/c dãy tỉ số bằng nhau, ta có:
\(\frac{a-b}{3}=\frac{a+b}{11}=\frac{a}{7}=\frac{b}{4}\)
\(\Rightarrow\frac{a}{7}=\frac{b}{4}=\frac{ab}{210}\)
Đặt \(\frac{a}{7}=\frac{b}{4}=\frac{ab}{210}=k\)
\(\Rightarrow\hept{\begin{cases}a=7k\\b=4k\\ab=210k\end{cases}}\)
Do đó \(7k.4k=210k\)(vô lí)
Vậy không tồn tại a,b thỏa mãn
NT
0
NM
Nguyễn Minh Quang
Giáo viên
1 tháng 11 2021
1. ta có
\(\hept{\begin{cases}a+b=15\times2=30\\b+c=7\times2=14\\a+c=11\times2=22\end{cases}\Rightarrow2\left(a+b+c\right)=30+14+22=66}\)
vậy \(a+b+c=33\Rightarrow\hept{\begin{cases}c=33-30=3\\a=33-14=19\\b=33-22=11\end{cases}}\)
câu hai tương tự bạn nhé
NX
2
6 tháng 2 2017
(a + b) + (b + c) + (a + c) = 11 + 3 + 2
(a + a) + (b + b) + (c + c) = 16
2a + 2b + 2c = 16
2(a + b + c) = 16
=> a + b + c = 8
=> c = (a + b + c) - (a + b) = 8 - 11 = - 3
=> - 3 + b = 3 => b = 6
=> - 3 + a = 2 => a = 5
Vậy a = 5; b = 6; c = - 3
6 tháng 2 2017
ta co a+b=11,b+c=3,a+c=2
=a+b+b+c+a+c=11+3+2
=>2(a+b+c)=16
=>a+b+c=8
=>a=8-3==5
=>b=8-2=6
=>c=8-11=-3
8 tháng 12 2015
a) goi hai so la a ; b va a >b
vi UCLN(a,b)=18=>a=18k ; b=18q (trong do UCLN (k,q)=1 va k>q)
=>a+b=162
18k+18q =162
18(k+q)=162
k+q=9
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29 tháng 10 2016
21453
52542000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 | 542454550212.100000000000000000000000000000000000000000000000000000000000000000000000000000 |
S
0
NT
1
19 tháng 12 2015
a) 31x + (1+2+...+30) = 1240
31x + 31.15 = 1240
31x =1240 - 465
31x = 775
x= 25
b) (1+x) .x:2 = 210
(x+1)x =210.2 = 21.20
x =20
\(\frac{a.b}{210}=\frac{a-b}{3}=\frac{a+b}{11}\)
Áp dụng tính chất dãy tỉ số bằng nhau ta có:
\(\frac{a-b}{3}=\frac{a+b}{11}=\frac{a-b+a+b}{14}=\frac{a+b-\left(a-b\right)}{8}\)
\(\Rightarrow\frac{a-b}{3}=\frac{a+b}{11}=\frac{a}{7}=\frac{b}{4}\)
Đặt \(\frac{a}{7}=\frac{b}{4}=k\)\(\Rightarrow a=7k,b=4k\)
Thay vào ta có :
\(\frac{7k.4k}{210}=\frac{7k-4k}{3}=k\)
\(\Rightarrow28k^2=210k\)
+) Giả sử k = 0 = > a = b = 0 ( đúng )
+) Giả sử \(k\ne0\)= > \(28k=210\)
\(k=210:28=7,5\)
\(\Rightarrow a=7,5.7=52,5\)
\(b=7,5.4=30\)