1: Ta có: \(3\left(x+5\right)-2\left(4-3x\right)=7\)

\(\Leftrightarrow3x+15-8+6x=7\)

\(\Leftrightarrow9x=14\)

hay \(x=\dfrac{14}{9}\)

2: Ta có: \(x\left(7-2x\right)+2x\left(x-2\right)=15\)

\(\Leftrightarrow7x-2x^2+2x^2-4x=15\)

\(\Leftrightarrow3x=15\)

hay x=5

3: Ta có: \(2x\left(9x-4\right)-9x\left(2x-3\right)=-38\)

\(\Leftrightarrow18x^2-8x-18x^2+27x=-38\)

\(\Leftrightarrow19x=-38\)

hay x=-2

7: Ta có: \(\left(x-5\right)\left(x+5\right)-\left(x-5\right)^2=30\)

\(\Leftrightarrow x^2-5-x^2+10x-25=30\)

\(\Leftrightarrow10x=60\)

hay x=6

8: Ta có: \(\left(x+2\right)\left(x-2\right)+8=\left(x-1\right)^2\)

\(\Leftrightarrow x^2-4+8=x^2-2x+1\)

\(\Leftrightarrow-2x=3\)

hay \(x=-\dfrac{3}{2}\)

1D

2A

D, c

`@` `\text {Ans}`

`\downarrow`

`a)`

`-3x - 3/4 = 6/5`

`=> -3x = 6/5 + 3/4`

`=> -3x = 39/20`

`=> x = 39/20 \div (-3)`

`=> x = -13/20`

Vậy, `x=-13/20`

`b)`

`1/7 - 3/5x = 3/5`

`=> 3/5x = 1/7 - 3/5`

`=>3/5x = -16/35`

`=> x = -16/35 \div 3/5`

`=> x = -16/21`

`c)`

`3/7 - 1/2x = 5/3`

`=> 1/2x = 3/7 - 5/3`

`=> 1/2x = -26/21`

`=> x = -26/21 \div 1/2`

`=> x = -52/21`

Vậy, `x = -52/21`

`d)`

`-2/3x + 2 = 3/4`

`=> -2/3x = 3/4 - 2`

`=> -2/3x = -5/4`

`=> x = -5/4 \div (-2/3)`

`=> x = 15/8`

Vậy, `x=15/8.`

8 It took me 3 hours to do these exercise

9 Many years ago, my village used to be very poor

10 Mary last met him 5 years ago

11 Would you mind giving me a hand

12 There used to be many old buildings in this city

13 When were they married

14 I started learning Japanese 2 years ago

15 Jack used to be a good student

16  My sister used to buy all her clothes in Henry's

17 Braille is reading system for the blind

(2x+1)²+2(2+1)

=4x²+4x+1+4+2

=4x²+4x+7

a: Xét ΔBAE và ΔBDE có

BA=BD

\(\widehat{ABE}=\widehat{DBE}\)

BE chung

Do đó: ΔBAE=ΔBDE

b: Ta có: ΔBAE=ΔBDE

nên \(\widehat{BAE}=\widehat{BDE}=90^0\)

hay ED\(\perp\)BC

c: Xét ΔAKE vuông tại A và ΔDCE vuông tại D có

EA=ED

\(\widehat{AEK}=\widehat{DEC}\)

Do đó: ΔAKE=ΔDCE
Suy ra: EK=EC
hay ΔEKC cân tại E