Вычислите с подмогою формулы (а^2 -b^2)= (a-b)(a+b) номер 31.5

1) (13-9)(13+9)= 4*22=88

2)(20-19)(20+19)=1*39=39

3) (11/5)2-(14/5)2= 121/25 - 196/25= -3

4)(7/2)2 - (37/10)2= 49/4 - 1369/100= - 36/25 = -1 11/25= -1,44

5)25/36 - 4/9=1/4=0,25

6) 49/81-1/36=187/324

7) 25/144-9/16=-7/18

8) 9/100-16/25= -11/20=-0,55

9)64/225-16/25=-16/45

10) 0

11) (10/3)2-(21/5)2=100/9-441/25= - 1469/225 = - 6 119/225

12) (31/6)2-(22/3)2= 951/36-484/9= - 325/12= - 27 1/12

13) (51-41)(51+41)=10*92=920

14) (54-46)(54+46)= 8*100=800

15)(76-24)(76+24)=52*100=5200

16)(328-172)(328+172)=156*500=78000

17)(11/3)2-(7/3)2=121/9-49/9=8

18) (68/9)2-(40/9)2= 4624/81-1600/81=112/3=37,3