lm ho mik bai nay vs a
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Bài 4:
Ta có: \(\left(n+2\right)^2-\left(n-2\right)^2\)
\(=n^2+4n+4-n^2+4n-4\)
\(=8n⋮8\)
Bài 1:
a: \(x^2-12x+36=\left(x-6\right)^2\)
b: \(4x^2+12x+9=\left(2x+3\right)^2\)
c: \(\dfrac{1}{4}x^2-5xy+25y^2=\left(\dfrac{1}{2}x-5y\right)^2\)
d: \(\left(x-5\right)^2-16=\left(x-5-4\right)\left(x-5+4\right)=\left(x-9\right)\left(x-1\right)\)
e: \(25-\left(3-x\right)^2=\left(5-3+x\right)\left(5+3-x\right)=\left(x+2\right)\left(8-x\right)\)
g: \(\left(7x-4\right)^2-\left(2x+1\right)^2\)
\(=\left(7x-4-2x-1\right)\left(7x-4+2x+1\right)\)
\(=\left(5x-5\right)\left(9x-3\right)\)
\(=15\left(x-1\right)\left(3x-1\right)\)
f: \(8x^3+\dfrac{1}{27}=\left(2x+\dfrac{1}{3}\right)\left(4x^2-\dfrac{2}{3}x+\dfrac{1}{9}\right)\)
g: \(49\left(x-4\right)^2-9\left(x+2\right)^2\)
\(=\left(7x-28-3x-6\right)\left(7x-28+3x+6\right)\)
\(=\left(4x-34\right)\left(10x-24\right)\)
\(=4\left(2x-17\right)\left(5x-12\right)\)
rảnh ha ông nội
tui kb vs ông mà thấy ông có ib j âu
có mún bị chửi sml ko
bn nhớ tick cho mình nha
7a
bn ko chụp câu 8
9a
10c
11b
12d
13a
a) Ta có:
\(\widehat{xOy}+\widehat{OAz}=150^o+30^o=180^o\)
Mà 2 góc này ở vị trí trong cùng phía
\(\Rightarrow zz'//Oy\)
b) OM là phân giác của \(\widehat{xOy}\Rightarrow\widehat{MOA}=\dfrac{1}{2}\widehat{xOy}=\dfrac{1}{2}\cdot150^o=75^o\)
\(\widehat{OAz'}+\widehat{OAz}=180^o\) (kề bù)
\(\Rightarrow\widehat{OAz'}=180^o-30^o=150^o\)
ON là phân giác của \(\widehat{OAz'}\Rightarrow\widehat{OAN}=\dfrac{1}{2}\widehat{OAz'}=\dfrac{1}{2}\cdot150^o=75^o\)
\(\Rightarrow\widehat{MOA}=\widehat{OAN}=75^o\)
Mà 2 góc này ở vị trí đồng vị
⇒ OM//AN