=25(24+48)+75(16+56)

=72*25+72*75

=72*100

=7200

\(25.24+25.48+75.16+75.56\) 

\(=25.\left(24+48\right)+75.\left(16+56\right)\)

\(=25.72+75.72\)  

\(=\left(25+75\right).72\) 

\(=100.72\) 

\(=7200\)

a: =>4/3x=7/9-4/9=1/3

=>x=1/4

b: =>5/2-x=9/14:(-4/7)=-9/8

=>x=5/2+9/8=29/8

c: =>3x+3/4=8/3

=>3x=23/12

hay x=23/36

d: =>-5/6-x=7/12-4/12=3/12=1/4

=>x=-5/6-1/4=-10/12-3/12=-13/12

em moi lop 4 mà

\(d,-\dfrac{5}{6}-x=\dfrac{7}{12}+\dfrac{-1}{3}\)

\(\Leftrightarrow-\dfrac{5}{6}-x=\dfrac{7}{12}+\dfrac{-4}{12}\)

\(\Leftrightarrow-\dfrac{5}{6}-x=\dfrac{1}{4}\)

\(\Leftrightarrow-x=-\dfrac{5}{6}-\dfrac{1}{4}\)

\(\Leftrightarrow-x=-\dfrac{13}{12}\)

\(\Leftrightarrow x=\dfrac{13}{12}\)

\(c,3x+\dfrac{3}{4}=2\dfrac{2}{3}\)

\(\Leftrightarrow3x+\dfrac{3}{4}=\dfrac{8}{3}\)

\(\Leftrightarrow3x=\dfrac{8}{3}-\dfrac{3}{4}\)

\(\Leftrightarrow3x=\dfrac{23}{12}\)

\(\Leftrightarrow x=\dfrac{23}{12}:3\)

\(\Leftrightarrow x=\dfrac{23}{36}\)

em chịu_{em thua}

cái gì đây?

của bạn nè.Mik lớp 5 nhưng vẫn phải học thuộc hết 

\(2x-1-x^2\\ =x+x-1-x^2\\ =\left(x-x^2\right)+\left(x-1\right)\\ =-x\left(x-1\right)+\left(x-1\right)\\ =\left(x-1\right)\left(1-x\right)\)

2x - 1 - x²

= -x² + 2x - 1

= -(x² - 2x + 1)

= -(x - 1)²

Bài 3:

b: Xét ΔABC có

I là trung điểm của BC

IK//AC

Do đó: K là trung điểm của AB

Xét ΔABC có

I là trung điểm của BC

IH//AB

Do đó: H là trung điểm của AC

Xét ΔABC có 

K là trung điểm của AB

H là trung điểm của AC

Do đó: HK là đường trung bình của ΔABC

Suy ra: HK//BC

1 he didn't have to study for his exam

2 she weren't lazy, she could pass the exam

3 If my brother had left the car keys, I could have picked him up at the station

4 he pays me tonight, I will have enough money to buy a car

5 he didn't smoke too much, he could get rid of his cough

6 I hadn't lost my key, I wouldn't have had to pound on the door.....

7 she weren't shy, she would enjoy the party

8 I get a work permit, I will stay for another month

9 he took some exercises, he wouldn't be so unhealthy

10 those people had been prepared  to face the floods, the consequence wouldn't have been disastrous

11 she starts working hard now, she won't be able to pass the final test

12 you are patient, you won't get success

13 somebody waters these flowers. they will die

14 it doesn't stop raining, we won't go out

15 hhe hadn't drunk alcohol, he would have passed the contest