vậy bạn tự làm là đk mà

dat x-y=z

suy ra {3z^4+2z^3-5z^2}:z^2

dat nhan tu chung la z^2

=z^2(3z^2+2z-5)

minh chi bt the thoi

1 - {2 - [3 - 4.(5 - x)]} = 6

2 - [3 - 4.(5 - x)] = 1 - 6 = -5 

3 - 4.(5 - x) = 2- (-5) = 7

4.(5 - x) = 3 - 7 = -4 

5 - x = (-4) : 4 = -1 

x = 5 - (-1) 

x = 6 

Kết quả là bao nhiêu bạn ơi

Câu 3: 

a: \(\overrightarrow{BA}=\left(-2;6\right)\)

\(\overrightarrow{BC}=\left(3;1\right)\)

Vì \(\overrightarrow{BC}\cdot\overrightarrow{BA}=0\)

nên ΔABC vuông tại B

b: \(\overrightarrow{AB}=\left(2;-6\right)\)

\(\overrightarrow{AC}=\left(5;-5\right)\)

\(\cos\left(\overrightarrow{AB},\overrightarrow{AC}\right)=\dfrac{2\cdot5+6\cdot5}{\sqrt{2^2+6^2}\cdot\sqrt{5^2+5^2}}=\dfrac{2\sqrt{5}}{5}\)

\(-x-\frac{2}{3}=-\frac{6}{7}\)

\(\Leftrightarrow-x=-\frac{6}{7}+\frac{2}{3}\)

\(\Leftrightarrow-x=-\frac{4}{21}\)

\(\Leftrightarrow x=\frac{4}{21}\)

- Tks

70 - 5 x (X - 3) = 45

5 x (X - 3)=70-45

5 x (X - 3)=25

X - 3=25 : 5

X - 3=5

X=5+3

X=8

5 x ( x-3 ) = 70 - 45 = 35

      ( x-3 ) = 35 : 5 = 6

        x = 6 + 3 = 9

1) \(A=36x^2+12x+1=\left(6x+1\right)^2\ge0\)

\(minA=0\Leftrightarrow x=-\dfrac{1}{6}\)

2) \(B=9x^2+6x+1=\left(3x+1\right)^2\ge0\)

\(minB=0\Leftrightarrow x=-\dfrac{1}{3}\)

4) \(D=x^2-4x+y^2-8y+6=\left(x-2\right)^2+\left(y-4\right)^2-14\ge-14\) 

\(minD=-14\Leftrightarrow\left\{{}\begin{matrix}x=2\\y=4\end{matrix}\right.\)

3) \(C=\left(x+1\right)\left(x-2\right)\left(x-3\right)\left(x-6\right)=\left(x^2-5x-6\right)\left(x^2-5x+6\right)=\left(x^2-5x\right)^2-36\ge-36\)

\(minC\Leftrightarrow\left[{}\begin{matrix}x=0\\x=5\end{matrix}\right.\)

5) \(E=\left(x-8\right)^2+\left(x+7\right)^2=2x^2-2x+113=2\left(x-\dfrac{1}{2}\right)^2+\dfrac{225}{2}\ge\dfrac{225}{2}\)

\(minE=\dfrac{225}{2}\Leftrightarrow x=\dfrac{1}{2}\)

\(\left|x-\frac{5}{2}\right|+\frac{1}{6}=\frac{2}{3}\)

\(\left|x-\frac{5}{2}\right|=\frac{2}{3}-\frac{1}{6}\)

\(\left|x-\frac{5}{2}\right|=\frac{1}{2}\)

\(\Rightarrow\left[\begin{array}{nghiempt}x-\frac{5}{2}=\frac{1}{2}\\x-\frac{5}{2}=-\frac{1}{2}\end{array}\right.\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=3\\x=2\end{array}\right.\)

<=>|x-5/2|=2/3-1/6=1/2

=> x-5/2 =1/2   hoặc x-5/2=-1/2

* x-5/2=1/2<=>x=1/2+5/2=3

*x-5/2=-1/2<=>x=-1/2+5/2=2