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5²ˣ⁻³ - 2.5² = 5².3
5²ˣ⁻³ - 2.25 = 25.3
5²ˣ⁻³ - 50 = 75
5²ˣ⁻³ = 75 + 50
5²ˣ⁻³ = 125
5²ˣ⁻³ = 5³
2x - 3 = 3
2x = 3 + 3
2x = 6
x = 6 : 2
x = 3
64 . 52 + 37 . 52 - 2 . 26
= 64 . 52 + 37 . 52 - 52
=52 (64+37-1)
=52.100
=5200
52x-3 - 2 x 52 = 52 x3
52x-3 - 2x52 = 156
52x-3 - 104 = 156
52x-3 =156 + 104
52x-3 = 260
x-3 = 260:52
x-3 = 5
x=5+3
x=8
Vậy x=8
9*8*48+7*4*48+72*52+2*52*14
=72*48+28*48+72*52+28*52
=72 * ( 48 + 52 ) + 28 * ( 48 + 52 )
=72 * 100 + 28 * 100
=100 * ( 72 + 28 )
= 100 * 100
=10000
9 x 8 x 48 + 7 x 4 x 48 + 72 x 52 + 2 x 52 x 14
= 72 x 48 + 28 x 48 + 72 x 52 + 2 x 14 x 52
= ( 72 + 28 ) x 48 + 72 x 52 + 28 x 52
= ( 72 + 28 ) x 48 + ( 72 + 28 ) x 52
= 100 x 48 + 100 x 52
= 100 x ( 48 + 52 )
= 100 x 100
= 10000
\(B=\frac{1}{1\cdot2\cdot3}+\frac{1}{2\cdot3\cdot4}+\frac{1}{3\cdot4\cdot5}+\frac{1}{18\cdot19\cdot20}\)
\(B=\frac{1}{2}\left(\frac{2}{1\cdot2\cdot3}+\frac{2}{2\cdot3\cdot4}+\frac{2}{3\cdot4\cdot5}+\frac{2}{18\cdot19\cdot20}\right)\)
\(B=\frac{1}{2}\left(\frac{1}{1\cdot2}-\frac{1}{2\cdot3}+\frac{1}{2\cdot3}-\frac{1}{3\cdot4}+\frac{1}{3\cdot4}-\frac{1}{4\cdot5}+...+\frac{1}{18\cdot19}-\frac{1}{19\cdot20}\right)\)
\(B=\frac{1}{2}\left(\frac{1}{1\cdot2}-\frac{1}{19\cdot20}\right)\)
\(B=\frac{1}{2}\cdot\frac{189}{380}=\frac{189}{760}\)
\(C=\frac{52}{1\cdot6}+\frac{52}{6\cdot11}+\frac{52}{11\cdot16}+...+\frac{52}{31\cdot36}\)
\(C=\frac{52}{5}\left(\frac{5}{1\cdot6}+\frac{5}{6\cdot11}+\frac{5}{11\cdot16}+...+\frac{6}{31\cdot36}\right)\)
\(C=\frac{52}{5}\left(1-\frac{1}{6}+\frac{1}{6}-\frac{1}{11}+\frac{1}{11}-\frac{1}{16}+...+\frac{1}{31}-\frac{1}{36}\right)\)
\(C=\frac{52}{5}\cdot\left(1-\frac{1}{36}\right)\)
\(C=\frac{91}{9}\)
52: 2
= 25 : 2
= 12,5
52 : 2
= 25 : 2
= 12,5