\(205^2-95^2=\left(205-95\right)\left(205+95\right)=110.300=33000\)

Không bít xin lỗi nhiều

20565-9562=        11003

b, \(\left(2x-3\right)\left(x+1-x-5\right)=0\Leftrightarrow x=\dfrac{3}{2}\)

c, \(x^2-4x+1=2x-22\Leftrightarrow x^2-6x+23=0\Leftrightarrow\left(x-3\right)^2+14=0\left(voli\right)\)

pt vô nghiệm 

d, \(\dfrac{201-x}{99}+1+\dfrac{203-x}{97}+1=\dfrac{205-x}{95}+1\)

\(\Leftrightarrow\dfrac{300-x}{99}+\dfrac{300-x}{97}=\dfrac{300-x}{95}\)

\(\Leftrightarrow\left(300-x\right)\left(\dfrac{1}{99}+\dfrac{1}{97}-\dfrac{1}{95}\ne0\right)=0\Leftrightarrow x=300\)

\(\text{b) 205 + ( 2003 + 95)}\) 

\(=205+2098\) 

\(=2303\)

`@` `\text {Ans}`

`\downarrow`

Tính nhanh c nhỉ?

`b)`

`205 + (2003 + 95)`

`= 205 + 2003 + 95`

`= (205+95) + 2003`

`= 300 + 2003`

`= 2303`

a) 25² - 15²

= (25 - 15).(25 + 15)

= 10.40

= 400

b) 36² - 14²

= (36 + 14).(36 - 14)

= 50.22

= 1100

d) 950² - 850²

= (950 + 850).(950 - 850)

= 1 800.100

= 180 000

Tất cả đều dùng HĐT đáng nhớ (3) nha!(có trong SGK 8-tập 1)

Mk chỉ làm câu a thôi nha

\(a;25^2-15^2=\left(25-15\right)\left(25+15\right)\)

Giải:

Ta có: \(\frac{201-x}{99}+\frac{205-x}{95}+\frac{203-x}{97}+3=0\)

\(\Leftrightarrow\frac{201-x}{99}+1+\frac{205-x}{95}+1+\frac{203-x}{97}+1=0\)

\(\Leftrightarrow\frac{300-x}{99}+\frac{300-x}{95}+\frac{300-x}{97}=0\)

\(\Leftrightarrow\left(300-x\right)\left(\frac{1}{99}+\frac{1}{95}+\frac{1}{97}\right)=0\)

\(\Leftrightarrow300-x=0\) (Vì \(\frac{1}{99}+\frac{1}{95}+\frac{1}{97}\ne0\))

\(\Leftrightarrow x=300\)

Vậy phương trình có nghiệm là \(x=300.\)

Chúc bạn học tốt@@

`(201-x)/99+(203-x)/97+(205-x)/95+3=0`

`<=>(201-x)/99+1+(203-x)/97+1+(205-x)/95+1=0`

`<=>(300-x)/99+(300-x)/97+(300-x)/95=0`

`<=>(300-x)(1/99+1/97+1/95)=0`

`<=>300-x=0`

`<=>x=300`

Vậy `x=300`

Sai đề.

Vì 205-x/95+3=0

=>205-x/95=0-3=-3

=>205-x=-3*95=-285

=>x=205-(-285)=490

Vậy x=490

\(\Leftrightarrow\left(\dfrac{201-x}{99}+1\right)+\left(\dfrac{203-x}{97}+1\right)+\left(\dfrac{205-x}{95}+1\right)=0\)

=>300-x=0

=>x=300

<=> 300-x/99+300-x/97+300-x/95=0

<=>(300-x).(1/99+1/97+1/95)=0

<=>300-x=0

<=>x=300

25² - 15²

= (25 - 15)(25 + 15)

= 10 . 40

= 400

205² - 95²

= (205 - 95)(205 + 95)

= 110 . 300

= 33 000

36² - 14²

= (36 - 14)(36 + 14)

= 22 . 50

= 1 100

950² - 850²

= (950 - 850)(950 + 850)

= 100 . 1 800

= 180 000