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a) -4x2 + 8x - 4
= - (4x2 - 8x + 4)
= - (2x - 2)2
b) -x52 + 10 x - 5
= - 5(x2 - 2x + 1)
= - 5(x - 1)2
\(a,3x\left(x-4\right)-2x+8=0\)
\(\Rightarrow3x\left(x-4\right)-2\left(x-4\right)=0\)
\(\Rightarrow\left(3x-2\right)\left(x-4\right)=0\)
\(\Rightarrow\orbr{\begin{cases}3x-2=0\\x-4=0\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{2}{3}\\4\end{cases}}}\)
Vậy \(x=\frac{2}{3}\)hoặc \(x=4\)
\(b,\left(3x-1\right)^2-\left(3x+2\right)\left(3x+1\right)=2\)
\(\Rightarrow9x^2-6x+1-\left(9x^2+3x+6x+1\right)-2=0\)
\(\Rightarrow9x^2-6x+1-9x^2-3x-6x-1-2=0\)
\(\Rightarrow-15x-2=0\)
\(\Rightarrow-15x=2\)
\(\Rightarrow x=\frac{-2}{15}\)
\(8x\left(x-2\right)-3\left(x^2-4x-5\right)-5x^2\)
\(=8x^2-16x-3x^2+12x+15-5x^2\)
\(=15-4x\)
`8x(x-2) -3 (x^2 -4x-5)-5x^2`
`= 8x^2 - 16x - 3x^2 +12x+15 - 5x^2`
`= (8x^2 - 3x^2 - 5x^2)+(-16x +12x)+15`
`= -4x +15`
=(2x+2)2-9
vậy GTNN là -9
mình làm hơi tắt nhưng chắc bạn hiểu mà !!!
\(3\left(4x-5\right)^2-8x+10=0\)
<=> \(3\left(16x^2-40x+25\right)-8x+10=0\)
<=> \(48x^2-120x+75-8x+10=0\)
<=> \(48x^2-128x+85=0\)
<=> \(48x^2-68x-60x-85=0\)
<=> \(48x\left(x-\frac{17}{12}\right)-60\left(x-\frac{17}{12}\right)=0\)
<=> \(\left(48x-60\right)\left(x-\frac{17}{12}\right)=0\)
<=> \(\hept{\begin{cases}48x-60=0\\x-\frac{17}{12}=0\end{cases}}\)
<=> \(\hept{\begin{cases}x=\frac{5}{4}\\x=\frac{17}{12}\end{cases}}\)
a) 6x2 -11x -10
= 6x2 -15x +4x -10
= 3x(2x-5) + 2(2x-5)
= (2x-5)(3x+2)
( 4x - 5 ) 2 - 2( 4x - 5 ) = 0
<=> ( 4x - 5 ) ( 4x - 5 - 2 ) = 0
<=> ( 4x - 5 ) ( 4x - 7 ) = 0
\(\Leftrightarrow\orbr{\begin{cases}4x-5=0\\4x-7=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=\frac{5}{4}\\x=\frac{7}{4}\end{cases}}}\)
(4x-5)2 - 8x + 10 = 0
(4x-5)2 - 2.(4x-5) = 0
(4x-5).(4x-5 -2) = 0
(4x-5).(4x-7) = 0
=> 4x-5 = 0 => 4x = 5 => x = 5/4
4x-7 = 0 => 4x = 7 => x = 7/4
KL:...
\(3\left(4x-5\right)^2-8x+10=0\)
\(\Leftrightarrow\)\(3\left(4x-5\right)\left(4x-5\right)-2\left(4x-5\right)=0\)
\(\Leftrightarrow\)\(\left(4x-5\right)\left[2\left(4x-5\right)-2\right]=0\)
\(\Leftrightarrow\)\(\left(4x-5\right)\left(8x-10-2\right)=0\)
\(\Leftrightarrow\)\(\left(4x-5\right)\left(8x-12\right)=0\)
\(\Leftrightarrow\)\(\orbr{\begin{cases}4x-5=0\\8x-12=0\end{cases}}\)
\(\Leftrightarrow\)\(\orbr{\begin{cases}x=\frac{5}{4}\\x=1,5\end{cases}}\)
Vậy...
k mk đi
ai k mk
mk k lại
thanks