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a) =21.72 -11.72 +90.72 + 72.125.16
=72.(21-11+90+125.16)
=72 .2100
=102900
b)
=\(\frac{5.2^{30}.3^{18}-2^2.3^{20}.2^{27}}{5.2^9.2^{19}.3^{19}-7.2^{29}.3^{18}}\)
=\(\frac{5.2^{30}.3^{18}-2^{29}.3^{20}}{5.2^{28}.3^{19}-7.2^{29}.3^{18}}\)
=\(\frac{2^{29}.3^{18}.\left(5.2-3^2\right)}{2^{28}.3^{18}.\left(5.3-7.2\right)}\)
=\(\frac{2\left(5.2-3^2\right)}{5.3-7.2}\)
=\(\frac{2\left(10-9\right)}{15-14}=\frac{2.1}{1}=2\)
\(\frac{5.4^{15}.9^9-4.3^{20}.8^9}{5.2^9.6^{19}-7.2^{29}.27^6}\)\(=\frac{5.2^{30}.3^{18}-2^2.3^{20}.2^{27}}{5.2^9.2^{19}.3^{19}-7.2^{29}.3^{18}}\)\(=\frac{5.2^{30}.3^{18}-2^{29}.3^{20}}{5.2^{28}.3^{19}-7.2^{29}.3^{18}}\)\(=\frac{2^{29}.3^{18}\left(5.2-3^2\right)}{2^{28}.3^{18}\left(5.3-7.2\right)}=\frac{2.1}{1}=2\)
học tốt ~~~
\(\frac{5\cdot4^{15}\cdot9^9-4\cdot3^{20}\cdot8^9}{5\cdot2^9\cdot6^{19}-7\cdot2^{29}\cdot27^6}\\ =2\)
Xét tử :
5.415.99 - 4.320.89
= 5.230.318 - 22 . 320 . 227
= 5 . 230 . 318 - 229 . 320
= 318 . 220 . ( 5 . 210 - 29 . 32 )
= 318 . 220 . [ 29 . ( 5 . 2 - 32 ) ]
= 318 . 220 . 29
= 318 . 229
Xét mẫu :
5.29.619 - 7.229.276
= 5 . 29 . 219 . 319 - 7 . 229 . 318
= 5 . 228 . 319 - 7 . 229 . 318
= 318 . 228 . ( 5 . 3 - 7 . 2 )
= 318 . 228
B = \(\frac{3^{18}.2^{29}}{3^{18}.2^{28}}=2\)