Question

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​

Answer 1

Ответ:

Пошаговое объяснение:

1) $38^{2}$ - $28^{2}$ = (38-28)(38+28)=10*66=660

2)$74^{2}$-$26^{2}$ =(74-26)(74+26)=48*100=4800

3)$54^{2}$-$44^{2}$=(54-44)(54+44)=10*98=980

4)$165^{2}$-$65^{2}$ = (165-65)(165+65)=100*230=23000

5)$248^{2}$-$152^{2}$ = (248-152)(248+152)=96*400=96*100*4=9600*4=38400

6) $74.6^{2}$-$24.4^{2}$ =(74.6-24.4)(74.6+24.4)=50.2*99=50.2*100-50.2=5020-50.2=4969.8

7)$42.4^{2}$-$42.3^{2}$ = (42.4-42.3)(42.4+42.3)=0.1*84.7=8.47

8) $(8\frac{3}{4}) ^{2}$ - $(1\frac{1}{4} )^{2}$ = (8$\frac{3}{4}$ - 1$\frac{1}{4}$)(8$\frac{3}{4}$ + 1$\frac{1}{4}$)=($\frac{35}{4}$-$\frac{5}{4}$)($\frac{35}{4}$+$\frac{5}{4}$) = $\frac{30}{4}$*$\frac{40}{4}$=$\frac{30*10}{4}$=$\frac{300}{4}$=75