вычислите : 1) 38²-28² 2) 74²-26² 3) 54²-44² 4) 165²-65² 5) 248²-152² 6) 74,6²-24,4² 7) 42,4²-42,3² 8) (8 3/4 )² -(1 1/4)²

Пошаговое объяснение:

1) - = (38-28)(38+28)=10*66=660

2)- =(74-26)(74+26)=48*100=4800

3)-=(54-44)(54+44)=10*98=980

4)- = (165-65)(165+65)=100*230=23000

5)- = (248-152)(248+152)=96*400=96*100*4=9600*4=38400

6) - =(74.6-24.4)(74.6+24.4)=50.2*99=50.2*100-50.2=5020-50.2=4969.8

7)- = (42.4-42.3)(42.4+42.3)=0.1*84.7=8.47

8) - = (8 - 1)(8 + 1)=(-)(+) = *===75

(5/8)×x  +  (45/100)×x = 344

(5/8)×x  + (9/20)×x = 344

(100 + 72)/ 160 = 344

(172 / 160)×x = 344

x = (344×160)/172 = 320