\(\dfrac{5}{9}-\dfrac{1}{4}=\dfrac{20}{36}-\dfrac{9}{36}=\dfrac{11}{36}\)

\(\dfrac{49}{50}-\dfrac{4}{25}=\dfrac{49}{50}-\dfrac{8}{50}=\dfrac{41}{50}\)

help help !!

11/36

41/50

\(y\in\left(-\infty;\infty\right)\)

\(-2y^2-3xy-2y+2x^2+6x=1\)

\(-2y^2-3xy-2y-2x^2+6x-1=0\)

\(-2y^2-\left(3x+2\right)y+2x^2+6x-1=0\)

\(y=\frac{\sqrt{25x^2+60x-4-3x-2}}{4}\)

\(y=-\frac{\sqrt{25x^2+60x-4+3x+2}}{4}\)

#Ứng Lân

\(\dfrac{1}{1\cdot3}+\dfrac{1}{3\cdot5}+\dfrac{1}{5\cdot7}+...+\dfrac{1}{\left(2x-1\right)\cdot\left(2x+1\right)}=\dfrac{49}{99}\)

\(\dfrac{2}{1\cdot3}+\dfrac{2}{3\cdot5}+\dfrac{2}{5\cdot7}+...+\dfrac{2}{\left(2x-1\right)\cdot\left(2x+1\right)}=\dfrac{98}{99}\)

\(1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+....+\dfrac{1}{2x-1}-\dfrac{1}{2x+1}=\dfrac{98}{99}\)

\(1-\dfrac{1}{2x+1}=\dfrac{98}{99}\)

\(\dfrac{2x+1-1}{2x+1}=\dfrac{98}{99}\)

\(\dfrac{2x}{2x+1}=\dfrac{98}{99}\)

=> 2x=98

=> x=49

Câu 2: 

\(\left(A\cup B\right)\cap C=A\cap C=[1;+\infty)\cap\left(0;4\right)=[1;4)\)

Tập này có 3 phần tử nguyên

a,2 giờ 40 phút +25 phút nhân 3

b, 5 giờ 12 phút nhân 2 - 4 giờ

c,[ 2 giờ 45 phút +49 phút ] nhân 4

d,[ 8 giờ 15 phút ] :5 + 1 giờ 24 phút

\(2x^2-1=49\)

\(2x^2=49+1\)

\(2x^2=50\)

\(x^2=50:2\)

\(x^2=25\)

\(\Rightarrow\left\{{}\begin{matrix}x^2=5^2\\x^2=\left(-5\right)^2\end{matrix}\right.\)

\(\Rightarrow\left\{{}\begin{matrix}x=5\\x=-5\end{matrix}\right.\) \(\left(TM\right)\)

Vậy \(x\in\left\{5;-5\right\}\) là giá trị cần tìm

\(2x^2-1=49\)

\(2x^2=49+1\)

\(2x^2=50\)

\(x^2=25\)

\(x={5;-5}\)

2 x ² - 1 = 49

2 x ² = 49 + 1

2 x ² = 50

x ² = 25

x = 5 : - 5

7^2 . 7^x = 7^4

7^x = 7^2

=> x= 2

49 . 7^X = 2401

<=> 7² . 7^X  = 7⁴

=> 7^X = 7⁴ : 7²

<=> 7^X = 7² => X= 2

\(7^x=\frac{2401}{49}\)

\(7^x=49\)

\(7^x=7^2\)

x = 2

49:5=9(dư 4)

55:7=7(dư 6)

36:4=9

= 9 (dư 4)

= 7 (dư 6)

= 9

tk giúp mik nha

Bài 1: Rút gọn

\(A=\dfrac{-56\cdot49+\left(-49\right)\cdot44}{73\cdot14+\left(-14\right)\cdot\left(-27\right)}\)

\(=\dfrac{49\cdot\left(-56-44\right)}{14\cdot\left(73+27\right)}\)

\(=\dfrac{-49\cdot100}{14\cdot100}=\dfrac{-7}{2}\)