K
Khách
Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
PT
1

LD
1


18 tháng 11 2020
6a( x - 3y ) - 8b( 3y - x )
= 6a( x - 3y ) + 8b( x - 3y )
= 2( x - 3y )( 3a + 4b )
19 tháng 11 2020
\(6a\left(x-3y\right)-8b\left(3y-x\right)\)
\(=6a\left(x-3y\right)+8b\left(x-3y\right)\)
\(=\left(6a+8b\right)\left(x-3y\right)=2\left(3a+4b\right)\left(x-3y\right)\)
NN
0

DN
0

\(P=\left(x^2+4x+1\right)^2-12\left(x+2\right)^2+2093\)
\(=\left(x^2+4x+4-3\right)^2-12\left(x+2\right)^2+2093\)
\(=\left[\left(x+2\right)^2-3\right]^2-12\left(x+2\right)^2+2093\)
\(=\left(x+2\right)^4-6\left(x+2\right)^2+9-12\left(x+2\right)^2+2093\)
\(=\left(x+2\right)^4-18\left(x+2\right)^2+2102\)
\(=\left(x+2\right)^4-18\left(x+2\right)^2+81+2021\)
\(=\left[\left(x+2\right)^4-18\left(x+2\right)^2+81\right]+2021\)
\(=\left[\left(x+2\right)^2-9\right]^2+2021\)
\(=\left[\left(x+2-3\right)\left(x+2+3\right)\right]^2+2021\)
\(=\left[\left(x-1\right)\left(x+5\right)\right]^2+2021\)
Vì \(\left[\left(x-1\right)\left(x+5\right)\right]^2\ge0\forall x\)
\(\Rightarrow\left[\left(x-1\right)\left(x+5\right)\right]^2+2021\ge2021\)\(\forall x\)
hay \(P\ge2021\)
Dấu " = " xảy ra \(\Leftrightarrow\left(x-1\right)\left(x+5\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-1=0\\x+5=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=1\\x=-5\end{cases}}\)
Vậy \(minP=2021\)\(\Leftrightarrow\orbr{\begin{cases}x=1\\x=-5\end{cases}}\)