a) \(82^2-18^2=\left(82-18\right)\left(82+18\right)=64.100=6400\)
b) \(26^2+52.24+24^2=26^2+2.26.24+24^2=\left(26+24\right)^2=50^2=2500\)
c) \(\dfrac{93^3+78^3}{171}-93.78=\dfrac{\left(93+78\right)\left(93^2-93.78+73^2\right)}{171}-93.78\)
\(=\dfrac{171\left(93^2-93.78+73^2\right)}{171}-93.78\)
\(=93^2-93.78+73^2-93.78\)
\(=93^2-2.93.78+73^2=\left(93-73\right)^2=20^2=400\)
Câu C Cô Hoài Thương nhầm chỗ \(93^3+78^3=\left(93+78\right)\left(93^2-93.78+78^2\right)\)
không phải \(\left(93+78\right)\left(93^2+93.78+78^2\right)\)
a, 822 - 182 = (82 - 18).(82+18) = 64.100 = 6400
b, 262 + 54.24 + 242 = (26 + 24)2 = 502 =2500
c, \(\dfrac{93^3+78^3}{171}\) - 93.78
= \(\dfrac{\left(93+78\right).\left(93^2-93.78+78^2\right)}{171}\) - 93.98
= \(\dfrac{171.\left(93^2-93.78+78^2\right)}{171}\) - 93.98
= 932 - 93.78 + 782 - 93.78
= (93 - 78)2
= 152 = 225
d, \(\dfrac{57^2-18^2}{76,5^2-1,5^2}\)
= \(\dfrac{\left(57-18\right)\left(57+18\right)}{\left(76,5-1,5\right).\left(76,5+1,5\right)}\)
= \(\dfrac{39.75}{75.78}\)
= \(\dfrac{1}{2}\)
