13-12+11+10-9+8-7-6+5-4+3+2-1

=(13-12+11+10-9)+(8-7-6+5)+(-4+3+2-1)

=13+0+0=13

mình cũng đang vướng mắc hai câu này

chắc bạn nguyễn thu hà đi thi hsg toán 6 đúng không

\(b)\) \(1.2.3...9-1.2.3...8-1.2.3...8^2\)

\(=\)\(1.2.3...8\left(9-1-8\right)\)

\(=\)\(1.2.3...8\left(9-9\right)\)

\(=\)\(1.2.3...8.0\)

\(=\)\(0\)

a)\(\left(10^2+11^2+12^2\right)\div\left(13^2+14^2\right)\)

\(=\left(100+121+144\right)\div\left(169+196\right)\)

\(=365\div365\)

\(=1\)

b) \(1.2.3...9-1.2.3...8-1.2.3...8^2\)

\(=1.2.3...8\left(9-1-8\right)\)

\(=1.2.3...8.0\)

\(=0\)

d) \(1152-\left(374+1152\right)+\left(-65+374\right)\)

\(=1152-374-1152-65+374\)

\(=\left(1152-1152\right)-65+\left(374-374\right)\)

\(=0-65+0\)

\(=-65\)

e) \(13-12+11+10-9+8-7-6+5-4+3+2-1\)

\(=13-\left(12-11\right)+\left(10-9\right)+\left(8-7\right)-\left(6-5\right)-\left(4-3\right)\)\(+\left(2-1\right)\)

\(=13-1+1+1-1-1+1\)

\(=13+0+0+0\)

\(=13\)

Câu a:

(7\(^{2017}\) - 7\(^{2015}\)) ⋮ (7\(^{2014}\).7)

= 7\(^{2015}\).(7\(^2\) - 1) ⋮ 7\(^{2015}\)

= (7\(^{2015}\) : 7\(^{2015}\)).(49 - 1)

= 1.48

= 48

Câu b:

(2\(^{13}\) + 2\(^5\)) : (2\(^{10}\) + 2\(^2\))

= 2\(^5.\)(2\(^8\) + 1):[2\(^2\).(2\(^8\) + 1)]

= (2\(^5:2^2\)).[(\(2^8+1):\left(2^8+1\right)\)]

= 2\(^3\).1

= 8