1.3.5.7...99=5/2.5/2.5/2...100/2
Tính:
\(S=1+2.5+2.5^2+3.5^3+...+100.5^{99}\)
Điền dấu >,<, = thích hợp vào ô trống
\(\dfrac{15}{100}\) .................. 115 %
\(\dfrac{5}{2}\) ................ 2.5
\(\dfrac{15}{100}=0,15\)
\(115\%=\dfrac{115}{100}=1,15\)
Mà \(0,15< 1,15\)
Vậy \(\dfrac{15}{100}< 115\%\)
____________
\(\dfrac{5}{2}=2,5\)
Vậy \(\dfrac{5}{2}=2,5\)
\(\dfrac{15}{100} = 115% \)%
\(\dfrac{5}{2}=2,5\)
so sánh 1.3.5.7.....99 và 51/2.52/2.53/2.....100/2
C=1.3.5.7.....99 và D=51/2.52/2.53/2....100/2
12 :{390:[2.5^2-(5^3+7^2.5)]}
so sánh 1.3.5.7....99 với d=51/2 .52/2 .53/2 .....100/2
So sanh : A=1.3.5.7...99 va B =51/2.52/2...100/2
\(A=\frac{1.2.3...........99.100}{2.4.6....100}\)
\(=\frac{1.2.3..............99.100}{1.2.2.2.2.3.........50.2}\)
\(=\frac{1.2.3.......50........99.100}{\left(1.2.3........50\right).2.2.....2}\)
\(=\frac{51.52..........99.100}{2.2............2}\)
\(=\frac{51}{2}.\frac{52}{2}...........\frac{100}{2}\)
So sanh S=1.3.5.7....99 với D=51/2.52/2.....100/2
c) {[(20 - 2.3).5] - 2.5} : 2 + (4.5)²
= {(20 - 6).5] - 10} : 2 + 20²
= (14.5 - 10) : 2 + 400
= (70 - 10) : 2 + 400
= 60 : 2 + 400
= 30 + 400
= 430
d) (1² + 2² + 3² + ... + 100²) . (2⁴ - 4²)
= (1² + 2² + 3² + ... + 100²) . (16 - 16)
= (1² + 2² + 3² + ... + 100²) . 0
= 0
Bài 2
a) -2x < 5
2x > 5
x > 5/2
b) [31 - (x + 5)].11 = 121
31 - (x + 5) = 121 : 11
31 - (x + 5) = 11
x + 5 = 31 - 11
x + 5 = 20
x = 20 - 5
x = 15
c) (x + 1)³ = 27
(x + 1)³ = 3³
x + 1 = 3
x = 3 - 1
x = 2