a) Vì \(\widehat{xOy}< \widehat{xOz}\left(50^o< 100^o\right)\)

Nên tia Oy nằm giữa 2 tia Ox và Oz

\(\Rightarrow\widehat{xOz}=\widehat{xOy}+\widehat{yOz}\)

\(\Rightarrow\widehat{yOz}=\widehat{xOz}-\widehat{xOy}=100^o-50^o=50^o\)

b)Vì tia Oy nằm giữa 2 tia Ox và Oz và \(\widehat{xOy}=\widehat{yOz}=50^o\)

Nên Oy là tia phân giác của \(\widehat{xOz}\)

c) Vì tia Ot là tia đối của tia Ox nên \(\widehat{xOt}=180^o\)và tia Oy nằm giữa 2 tia Ox và Ot

\(\Rightarrow\widehat{xOt}=\widehat{xOy}+\widehat{yOt}\)

\(\Rightarrow\widehat{yOt}=\widehat{xOt}-\widehat{xOy}=180^o-50^o=130^o\)

bài3 a)-11 b)-35
bài4 a)-5/3 b)-3/5 c)7/-8

Answer:

\(A=\frac{17^{18}+1}{17^{19}+1}\)

\(\Rightarrow17A=\frac{17^{19}+17}{17^{19}+1}=\frac{17^{19}+1+16}{17^{19}+1}=1+\frac{16}{17^{19}+1}\)

\(B=\frac{17^{17}+1}{17^{18}+1}\)

\(\Rightarrow17B=\frac{17^{18}+17}{17^{18}+1}=\frac{17^{18}+1+16}{17^{18}+1}=1+\frac{17}{17^{18}+1}\)

Mà \(17^{18}< 17^{19}\)

\(\Rightarrow17^{18}+1< 17^{19}+1\)

\(\Rightarrow\frac{16}{17^{18}+1}>\frac{16}{17^{19}+1}\)

\(\Rightarrow1+\frac{16}{17^{18}+1}>1+\frac{16}{17^{19}+1}\)

Vậy A < B

b) 2³.3 - (1¹⁰ + 15) : 4²

= 8 . 3 - 16 : 16

= 24 - 1 

= 23

c) 21.[(1 245 + 987):2³ – 15.12] + 21 

= 21 . [2232 : 8 - 180] + 21

= 21 . 99 + 21

= 21 . ( 99 + 1 )

= 21 . 100 

= 2100

d) 321 – 21.[(2.3³ + 4⁴:32) – 52].

= 321 - 21. [54 + 8 - 52 ]

= 321 - 21 . 10

= 321 - 210

= 111

b,)2³.3 - (1¹⁰ + 15):4²

=8 . 3 - 16 : 16

= 24 - 1

= 23

c) 21.[(1 245 + 987):2³ - 15.12] + 21

=21.[2232 : 8 - 180] + 21

=21.99+21

=21.(99+1)

=21.100

=2100

=12 000 000 + (12 000 000*10%)=13 200 000

Tiền thuế VAT là:12000000.10%=120000(đồng)
Gía tiền 1 chiếc máy giặt khi bán ra là:12000000+120000=1320000(đồng)
Đáp số:132000đồng

\(\frac{31}{100}.x=372\Leftrightarrow x=372:\frac{31}{100}=1200\)

HT

\(\frac{11}{3}.x=-286\Leftrightarrow x=\left(-286\right):\frac{11}{3}=-78\)

HT

TL

\(\frac{11}{3}x=-286\)

\(\Leftrightarrow x=-286:\frac{11}{3}\)

     \(\Leftrightarrow x=-78\)

HT

ta có 17/-35=-17/35
(3/17+14/17)+(-5/13+-8/13)+(-18/35+-17/35)
=17/17+-17/17+-35/35
=1+-1+-1
=-1

\(\frac{1}{5}-\frac{-2}{3}-\frac{7}{10}=\)

\(\frac{1.6}{5.6}-\frac{(-2).10}{3.10}-\frac{7.3}{10.3}\)

= \(\frac{6}{30}-\frac{-20}{30}-\frac{21}{30}\)

= \(\frac{6}{30}+\frac{20}{30}-\frac{21}{30}\)

=\(\frac{6+20-21}{30}\)

= \(\frac{5}{30}\)

= \(\frac{1}{6}\)

HTTT