Решите ТРИГОНОМЕТРИЯ​

I.
1) 7*8 / 16*21 =1/2*3=1/6

2) 13/4 * 48/13 =13*48 /4*13
=12

3) 5/7 *(-21/10)= -5*21 /7*10
= -3/2= -1.5

4) 5*(-9) /9 = -5

5) 13/2 * 13/5 =13*13 /10=
=169/10=16.9

6) 81/100 :9/1000 =
= 81/100 * 1000/9=81*10/9=
=9*10=90
при делении на дробь мы ее переворачиваем и будет умножение

II.
1) -5*33 / 11*65 = -3/13

2) -16/3 * 3/2=-16*3/3*2= -8

3) -4/5: -16/15 = 4/5 *15/16=
=4*15 / 5*16 = 3/4

4) -4/5 * 1/9 = -4/5*9= -4/45

5) 5.3=53/10, 7.7=77/10
-53/10 * 77/10 = -53*77/100= -40.81

6) 1515/10000 : 5/100 =
=1515*100 / 10000*5 =
=303/100= 3.03

1) (4n-m)(4n+m)
2) (6a-7)(6a+7)
3) (8-12x)(8+12x)
4) (3m-9n)(3m+9n)
5) (11b-15d)(11b+15d)
6) (0.8n-0.5m)(0.8n+0.5m)
7) (3-bc)(3+bc)
8) (2ab-1)(2ab+1)
9) (9cd-6a)(9cd+6a)
10) (2x²-5b⁴)(2x²+5b⁴)
11) (8-a²b²)(8+a²b²)
12) (4bc⁶-0.5)(4bc⁶+0.5)
13) (0.9p⁴m²-0.1x⁷)(0.9p⁴m²+0.1x⁷)
14) (x+3-1)(x+3+1)=(x+2)(x+4)
15) (8-b-1)(8+b+1)=(7-b)(9+b)
16) (4a-3-4)(4a-3+4)=(4a-7)(4a+1)
17) (5a-3b-5b)(5a-3b+5b)=(5a-8b)(5a+2b)
18) (3-7-3d)(3+7+3d)=(-4-3d)(10+3d)
19) (m-n-m-n)(m-n+m+n)=-2n*2m=-4mn
20) (4c-x-2c-3x)(4c-x+2c+3x)=(2c-4x)(6c+2x)=2(c-2x)*2(3c+x)=
       =4(c-2x)(3c+x)