câu a:S

câu b:Đ

câu c:S

câu d:Đ

A. S

B. Đ

C. S

D. Đ

Cách 1 :

\(127.(-89)+89.27\)

\(= (-127).89+89.27\)

\(= 89.[(-127)+27]\)

\(=89.\left(-100\right)=-8900\)

Cách 2 :

\(127.(-89)+89.27\)

\(=-11303+2403=-8900\)

127 . ( - 89 ) + 89 . 27

= 127 . [( - 89 ) + 89 ] . 27

= 127 . 0 . 27

= 0 . 27

= 0

a) \(-\left(76-35+15\right)+\left[18-27+\left(-17\right)\right]\)

\(=-76+35+15+18-27-17\)

\(=-52\)

b) \(167+\left[127-235-\left(-16\right)\right]+\left(-67\right)\)

\(=167+127-235+16-67\)

\(=8\)

c) \(\left(-19\right)+165-\left[27+\left(-21\right)-\left(+72\right)\right]\)

\(=\left(-19\right)+165-27+21+72\)

\(=212\)

d) \(89.\left(-2\right)+\left[20+\left(-2\right).\left(-5\right)-85\right]\)

\(=\left(-178\right)+\left(20+10-85\right)\)

\(=\left(-178\right)+20+10-85\)

\(=-233\)

\(13-32+51-70+89-108+127-146+165\)

\(=\left(13+127\right)-\left(32+108\right)+\left(51+89\right)-\left(70+146-165\right)\)

\(=140-140+140-51\)

\(=140-51\)

\(=89\)

Mong mn giúp mình nhanh nha mik đang cần rất gấp gáp đó chiều nay mik đi học thêm rồi

\(A=\frac{9}{15.18}+\frac{9}{18.21}+.....+\frac{9}{89.92}\)

\(A=3.\left(\frac{3}{15.18}+\frac{3}{18.21}+....+\frac{3}{89.92}\right)\)

\(A=3.\left(\frac{1}{15}-\frac{1}{18}+\frac{1}{18}-\frac{1}{21}+......+\frac{1}{89}-\frac{1}{92}\right)\)

\(A=3.\left(\frac{1}{15}-\frac{1}{92}\right)\)

\(A=3.\frac{77}{1380}=\frac{77}{460}\)

$A=\frac{9}{15.18}+\frac{9}{18.21}+.....+\frac{9}{89.92}$

$A=3.\left(\frac{3}{15.18}+\frac{3}{18.21}+....+\frac{3}{89.92}\right)$