Câu 1 . A<B
Câu 2 .A<B

(100^99+99^100)^100

(100^100+99^100)^99

ta có : (100^99+99^100)^100=100^9900+99^10000

           (100^100+99^100)^99=100^9900+99^9900

=)100^9900=100^9900; 99^10000>99^9900(vì 10000>9900)

=)(100^99+99^100)^100>(100^100+99^100)^99

\(\frac{-4}{25}x^2=-1\)

=> \(x^2=\frac{25}{4}\)

=>\(x^2=\left(\frac{5}{2}\right)^2\)

=> \(x=\frac{5}{2}\)

Chúc bạn học tốt

Trả lời :

\(10-\frac{3}{8}\times\frac{1}{5}-\frac{3}{8}\times\frac{4}{5}\)

\(=10-\left(\frac{3}{8}\times\frac{1}{5}+\frac{3}{8}\times\frac{4}{5}\right)\)

\(=10-\frac{3}{8}\)

\(=\frac{77}{8}\)

10 -3/8 x 1/5 -3/8 x 4/5

=10-3/8x (1/5-4/5)

=10 - 3/8 x (-3/5)

=10 - (-9/40)

=10 + 9/40 

=40/40 + 9/40

=49/40

chúc bn học tốt

Trả lời:

\(\frac{x}{5}=\frac{5}{6}-\frac{1}{2}\)

\(\Leftrightarrow\frac{x}{5}=\frac{1}{3}\)

\(\Leftrightarrow3x=5\)

\(\Leftrightarrow x=\frac{5}{3}\)

Vậy \(x=\frac{5}{3}\)

\(\frac{x}{5}=\frac{5}{6}-\frac{1}{2}\)

\(\frac{x}{5}=\frac{5}{6}-\frac{3}{6}\)

\(\frac{x}{5}=\frac{1}{3}\)

\(\Leftrightarrow3x=5\)

\(\Leftrightarrow x=\frac{5}{3}\)

Vậy \(x=\frac{5}{3}\)

Học tốt

26 + 18x = 16x + 146

=> 18x - 16x = 146 - 26

=> 2x = 120

=> x = 60

Vậy: x = 60

Ta có : 26 + 18x = 16x + 146

=> 18x - 16x = 146 - 26

=> 2x = 120

=> x = 60

Vậy x = 60

Ta có B = 3 + 3² + 3³ + ... + 3²⁰¹⁴ + 3²⁰¹⁵

=> 3B = 3² + 3³ + 3⁴ + .... + 3²⁰¹⁵ + 3²⁰¹⁶

Lấy 3B trừ B theo vế ta có 

3B - B = (3² + 3³ + 3⁴ + .... + 3²⁰¹⁵ + 3²⁰¹⁶) - (3 + 3² + 3³ + ... + 3²⁰¹⁴ + 3²⁰¹⁵)

   2B   = 3²⁰¹⁶ - 3

Khi đó 2B + 3 = 3^x

<=>  3²⁰¹⁶ - 3 + 3 = 3^x

=> 3²⁰¹⁶ = 3^x

=> x = 2016 

Vậy x = 2016

Bg

Ta có: B = 3 + 3² + 3³ +...+ 3²⁰¹⁴ + 3²⁰¹⁵ 

=> 3B = 3.(3 + 3² + 3³ +...+ 3²⁰¹⁴ + 3²⁰¹⁵)

=> 3B = 3.3 + 3.3² + 3.3³ +...+ 3.3²⁰¹⁴ + 3.3²⁰¹⁵

=> 3B = 3² + 3³ + 3⁴ +...+ 3²⁰¹⁵ + 3²⁰¹⁶ 

=> 3B - B = (3² + 3³ + 3⁴ +...+ 3²⁰¹⁵ + 3²⁰¹⁶) - (3 + 3² + 3³ +...+ 3²⁰¹⁴ + 3²⁰¹⁵)

=> 2B = 3²⁰¹⁶ - 3

 2B + 3 = 3^x

=> 3²⁰¹⁶ - 3 + 3 = 3^x

=> 3²⁰¹⁶ = 3^x

=> x = 2016

1) a) \(\frac{2}{3}+\frac{1}{3}.x=1\)

=> \(\frac{1}{3}x=\frac{1}{3}\)

=> x = 1

b) 1 + 2 + 3 + .... + x = 325

=> x(x + 1) : 2 = 325

=> x(x + 1) = 650

=> x(x + 1) = 25.26

=> x = 25

2) A = 1 + 2 + 3 + .... + n

= [(n - 1) : 1 + 1] . (n + 1) : 2

= n.(n + 1) : 2

B = 2 + 4 + 6 + ... +  2n

= 2(1 + 2 + 3 + ... + n)

= 2.n(n + 1) : 2

= n(n + 1)

3) a) 1 + 3 + 5 + .... + (2x + 1) = 169

=> [(2x + 1 - 1) : 2 + 1] . (2x + 1 + 1) : 2 = 169

=> (x + 1).2(x + 1) : 2 = 169

=> (x + 1)² = 169

=> x + 1 = 13

=> x = 12

3) b (x + 1) + (x + 2) + (x + 3) .... + (x + 10) = 195 (10 cặp số)

=> (x + x + .... + x) + (1 + 2 + 3 + .... + 10) = 195

     10 hạng tử x          10 số hạng

=> 10x + 10(10 + 1) : 2 = 195

=> 10x + 55 = 195

=> 10x = 140

=> x = 14