\(\frac{15^{30}}{45^{15}}=\frac{\left(3.5\right)^{30}}{\left(9.5\right)^{15}}=\frac{3^{30}.5^{30}}{9^{15}.5^{15}}=\frac{3^{30}.5^{30}}{3^{2.15}.5^{15}}=\frac{3^{30}.5^{30}}{3^{30}.5^{15}}=5^{15}\)

@@ đấy là tính máy tính

\(\frac{15^{30}}{45^{15}}=\frac{\left(15^2\right)^{15}}{45^{15}}=\frac{225^{15}}{45^{15}}=5^{15}\)

`2/5 + 9/15= 2/5 + 3/5=5/5=1`

`15/45 + 25/30= 1/3 + 5/6= 2/6+5/6=7/6`

`28/32 + 45/72=7/8+ 5/8=12/8=3/2`

`8/28 + 5/30= 2/7 + 1/6= 12/42 + 7/42= 19/42`

12 + 12 = 24

10 + 30 = 40

61 - 50 = 11

15 + 15 = 30

98 - 15 = 83

12 + 45 = 57

36 + 45 = 80

tk mình nha 

24

40

11

30

83

57

81

chúc bạn học tốt HOSHIMIYA ICHIGO chào nhé

12+12= 24

10+30=40

61-50=11

15+15=30

98-15= 83

12+45= 57

36+45= 81

\(45.\left(15-30\right).45.45\)

\(=45.\left(-15\right).45.45\)

\(=-675.45.45\)

\(=-30375.45\)

\(=-1366875\)

45x(15-30)x45x45

=45x(-15)

=-675

Ta có:

\(\cos {15^0} = \cos \left( {{{45}^0} - {{30}^0}} \right) = \cos {45^0}\cos {30^0} + \sin {45^0}\sin {30^0} = \frac{{\sqrt 2 }}{2}.\frac{{\sqrt 3 }}{2} + \frac{{\sqrt 2 }}{2}.\frac{1}{2} = \frac{{\sqrt 6  + \sqrt 2 }}{4}\)

\(\sin {15^0} = \sin \left( {{{45}^0} - {{30}^0}} \right) = \sin {45^0}\cos {30^0} - \cos {45^0}\sin {30^0} = \frac{{\sqrt 2 }}{2}.\frac{{\sqrt 3 }}{2} - \frac{{\sqrt 2 }}{2}.\frac{1}{2} = \frac{{\sqrt 6  - \sqrt 2 }}{4}\)

\(\tan {15^0} = \tan \left( {{{45}^0} - {{30}^0}} \right) = \frac{{\tan {{45}^0} - \tan {{30}^0}}}{{1 + \tan {{45}^0}\tan {{30}^0}}} = \frac{{1 - \frac{{\sqrt 3 }}{3}}}{{1 + \frac{{\sqrt 3 }}{3}}} = 2 - \sqrt 3 \)

\(\cot {15^0} = \frac{1}{{\tan {{15}^0}}} = \frac{1}{{2 - \sqrt 3 }}\)

Bài 2:

\(a,45+170+25+30\)

\(=\left(45+25\right)+\left(170+30\right)\)

\(=60+200=260\)

Bài 3:

\(a,\left(x-6\right).5=150\)

\(x-6=150:5\)

\(x-6=30\)

\(x=30+6\)

\(x=36\)

\(b,2^5.\left(3x-2\right)=2^3.2^6\)

\(2^5.\left(3x-2\right)=2^{3+6}\)

\(2^5.\left(3x-2\right)=2^9\)

\(3x-2=2^9:2^5\)

\(3x-2=2^4=16\)

\(3x=16+2\)

\(3x=22\)

\(x=22:3\)

\(x\approx7,3\)

\(c,100-7.\left(x-5\right)=51\)

\(7.\left(x-5\right)=100-51\)

\(7.\left(x-5\right)=49\)

\(x-5=49:7\)

\(x-5=7\)

\(x=7+5\)

\(x=12\)

Phần d) bạn thiếu dữ liệu ạ.

Giúp với ạ 

Giúp với ạ 

a]27/45+25/15=3/5+5/3=34/15

b]28/32+45/72=7/8+5/8=12/8=3/2

c]8/28+5/30=2/7+1/6=19/42

`= 12 xx 45 + 12 xx 15 + 12 xx 30`

`= 12 xx (45+15+30)`

`= 12 xx 90`

`= 1080`.

a, 21.35-3.25.7=21.35-21.25=21.(35-25)=21.10=210

b, 77-11.(30+7)=77-330-77=-330

c, 85.(35-27)-35.(85-27)=85.35-85.27-35.85+35.27=0

d, 47.(45-15)-47.(45+15)=47.45-47.15-47.45-47.15=-2(47.15)=1410

a, 21.35-3.25.7=21.35-21.25=21.10=210

b,77-11.(30+7)=77-11.30-11.7=-11.30=-330

c,85.(35-27)-35.(85-27)=85.35-85.27-85.35+35.27=27.(-50)=-1350

d, 47.(45-15)-47.(45+15)=47.45-47.15-47.45-47.15=-47.30=-1410

a, 21 . 35 - 3 . 25 . 7

= (21 . 35) - (3 . 25 . 7)

= 735 - 525

= 210

b, 77-11.(30+7)

= 77 - 11.30 - 11.7

= -11.30

= -330

c, 85.(35-27)-35.(85-27)

= 85.35 - 85.27 - 85.35 + 35.27

= 27.(-50)

= -1350

d, 47.(45-15)-47.(45+15)

= 47.45 - 47.15 - 47.45 - 47.15

= -47.30

= -1410