Truong hop \(x=3\):

\(M\left(3\right)=\left(3\right)^2-4.3+3=0\Leftrightarrow x=3\) la nghiem cua da thuc \(M\left(x\right)\)(dpcm)

Truong hop \(x=-1\):

\(M\left(-1\right)=\left(-1\right)^2-4\left(-1\right)+3=9\Leftrightarrow x=-1\) khong la nghiem cua da thuc \(M\left(x\right)\)(dpcm)

E THANG KIA

\(\frac{1}{12}-\left(-\frac{1}{6}-\frac{1}{4}\right)\)

\(=\frac{1}{12}-\left(-\frac{2}{12}-\frac{3}{12}\right)\)

\(=\frac{1}{12}+\frac{2}{12}+\frac{3}{12}\)

\(=\frac{1}{2}\)

Thanks bạn cute Jeon Koo Koo nhìu nha , tớ cảm ơn pạn rất nhìu :3

x=6

y=10

Ta có \(\frac{x}{3}=\frac{y}{5}=\frac{x+y}{3+5}=\frac{16}{8}=2\)(dãy tỉ số bằng nhau) 

=> x = 3.2 = 6 ; 

y = 5.2 = 10

Vậy x = 6 ; y = 10 

a)

\(P\left(x\right)=x-2x^2+3x^5+x^4+x\)

\(\Leftrightarrow P\left(x\right)=\left(x+x\right)-2x^2+x^4+3x^5\)

\(\Leftrightarrow P\left(x\right)=2x-2x^2+x^4+3x^5\)

\(Q\left(x\right)=3-2x-2x^2+x^4-3x^5-x^4+4x^2\)

\(\Leftrightarrow Q\left(x\right)=3-2x+\left(-2x^2+4x^2\right)+\left(x^4-x^4\right)-3x^5\)

\(\Leftrightarrow Q\left(x\right)=3-2x+2x^2-3x^5\)

b)

\(P\left(x\right)+Q\left(x\right)=\left(2x-2x^2+3x^5+x^4\right)+\left(3-2x+2x^2-3x^5\right)\)

\(=2x-2x^2+3x^5+x^4+3-2x+2x^2-3x^5\)

\(=\left(2x-2x\right)+\left(3x^5-3x^5\right)+\left(-2x^2+2x^2\right)+x^4+3\)

\(=x^4+3\)

\(P\left(x\right)-Q\left(x\right)=\left(2x-2x^2+3x^5+x^4\right)-\left(3-2x+2x^2-3x^5\right)\)

\(=2x-2x^2+3x^5+x^4-3+2x-2x^2+3x^5\)

\(=\left(2x+2x\right)+\left(-2x^2-2x^2\right)+\left(3x^5+3x^5\right)+x^4-3\)

\(=4x-4x^2+6x^5+x^4-3\)

\(=6x^5+x^4-4x^2+4x-3\)