Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
để 2a76b chia hết cho 10 thì b = 0
Nếu b =0 thì 2a76b =2a760
để 2a760 chia hết cho 9 thì [ 2 + a + 7 + 6 + 0 ] chia hết cho 9
[ 15 + a ] chia hết cho 9
=> a = 3
Vậy : a = 3 và b = 0
a, ta có :
123/456 < 123/789 < 456/789
Từ đó suy ra 123/456< 456/789
k nha
a) \(A=\frac{135}{135.136-1}\) và \(B=\frac{136}{136.137-1}\)
\(A=\frac{1}{136-1}=\frac{1}{135}\) \(B=\frac{1}{137-1}=\frac{1}{136}\)
Vì \(\frac{1}{136}\)< \(\frac{1}{135}\)nên A > B.
a, A = \(\frac{136-1}{\left(136-1\right)136-1}\) = \(\frac{136-1}{136^2-136-1}\) B=\(\frac{136}{136\left(136+1\right)-1}\)=\(\frac{136}{136^2+136-1}\)
x=136, A-B =\(\frac{x-1}{x^2-x-1}\)-\(\frac{x}{x^2+x-1}\) =\(\frac{x^3+x^2-x-x^2-x+1-x^3+x^2+x}{\left(x^2-1\right)^2-x^2}\)=\(\frac{x^2-x+2}{\left(x^2-1\right)^2-x^2}\)<0
=> A<B
b,A = \(\frac{456-333}{456}\)= 1-333/456 B=\(\frac{789-333}{789}\)= 1-333/789
=> A>B
c, 3/14<3/13<3/12<3/11<3/10 <2/5
M = 3/10+3/11+3/12+3/13+3/14 < 2/5 x5 = 2= N
Bài 1:
a) 248 + (-12) + 2064 + (-236)
= 248 - 236 + 2064 - 12
= 12 + 2052
= 2064
b) (-298) + (-300) + (-302)
= -298 - 302 - 300
= -600 - 300
= -900
c) 5 + (-7) + 9 + (-11) + 13 + (-15)
= -2 - 2 - 2
= -6
d) (-6) + 8 + (-10) + 12 + (-14) + 16
= 2 + 2 + 2
= 6
e) 456 + [58 + (-456) + (-38)]
= 456 - 456 + 58 - 38
= 0 + 20
= 20
Bài 2:
a) 8 - (3 + 7)
= 8 - 3 - 7
= -2
b) (-5) - (9 - 12)
= -5 - 9 + 12
= -2
c) (5674 - 97) + (97 + 18 - 5674)
= 5674 - 97 + 97 + 18 - 5674
= 18
d) (13 - 135 + 49) - (13 + 49)
= 13 - 13 - 135 + 49 - 49
= -135
e) x + 8 - (x + 22)
= x + 8 - x - 22
= -14
f) - (x + 5) + (x + 10) - 5
= -x - 5 + x + 10 - 5
= 0
Đặt A = \(\frac{1}{1!}+\frac{1}{2!}+\frac{1}{3!}+...+\frac{1}{2015!}\)
A < \(1+\frac{1}{1.2}+\frac{1}{2.3}+....+\frac{1}{2014.2015}\)
A < \(1+1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+....+\frac{1}{2014}-\frac{1}{2015}\)
A < \(2-\frac{1}{2015}\)< 2 < \(2\left(\frac{135^2+136}{136^2-135}\right)\)
=> A < \(2\left(\frac{135^2+136}{136^2-135}\right)\)(Đpcm)
\(11\div\left\{\frac{7}{8}-3\cdot\left[0,25\div\left(1\frac{1}{3}+2\cdot\frac{1}{3}\right)\right]\right\}\)
\(=11\div\left\{\frac{7}{8}-3\cdot\left[\frac{1}{4}\div\left(\frac{4}{3}+2\cdot\frac{1}{3}\right)\right]\right\}\)
\(=11\div\left\{\frac{7}{8}-3\cdot\left[\frac{1}{4}\div\left(\frac{4}{3}+\frac{2}{3}\right)\right]\right\}\)
\(=11\div\left\{\frac{7}{8}-3\cdot\left[\frac{1}{4}\div2\right]\right\}\)
\(=11\div\left\{\frac{7}{8}-3\cdot\frac{1}{8}\right\}\)
\(=11\div\left\{\frac{7}{8}-\frac{3}{8}\right\}\)
\(=11\div\frac{1}{2}\)
\(=22\)
b) 101*789 + 456*128 - 789 + 912*436
= 789*100 + 456*128 + 912*436
= 789*100 + 912*64 + 912*436
= 789*100 + 912*500
= 100*(789 + 912*5)
= 100*5349
= 534900