Question

Tìm x

1) 3(x−1)2−3x(x−5)=1

2) (6x−2)2+(5x−2)2−4(3x−1)(5x−2)=0

3) (2x−5)(2x+5)−1=0

4) 5x2−20=0

Giusp mk vs

Answer 1

Mấy cái số 2 đằng sau ngoặc là mũ đấy các bạn 

Answer 2

\(a,3(x-1)^2-3x(x-5)=1\)

\(\Leftrightarrow3x^2-6x+3-3x^2-15x=1\)

\(\Leftrightarrow\left[3x^2-3x^2\right]+3-\left[15x-6x\right]=1\)

\(\Leftrightarrow3-9x=1\)

\(\Leftrightarrow9x=2\Leftrightarrow x=\frac{2}{9}\)

Answer 3

\(c,(2x-5)(2x-5)-1=0\)

\(\Leftrightarrow4x^2-20x+25=1\)

\(\Leftrightarrow(2x-5)^2=1\)

\(\Leftrightarrow(2x-5)^2=1^2=(-1)^2\)

\(\Leftrightarrow\orbr{\begin{cases}2x-5=1\\2x-5=-1\end{cases}}\Rightarrow\orbr{\begin{cases}x=3\\x=2\end{cases}}\)

Answer 4

\(d,5x^2-20=0\)

\(\Leftrightarrow5x^2=20\)

\(\Leftrightarrow x^2=4\)

\(\Leftrightarrow x=\pm2\)

Answer 5

\(\left(6x-2\right)^2+\left(5x-2\right)^2-4\left(3x-1\right)\left(5x-2\right)=0\)

\(\Leftrightarrow\left[2\left(3x-1\right)\right]^2+\left(5x-2\right)^2-4\left(3x-1\right)\left(5x-2\right)=0\)

\(\Leftrightarrow\left[2\left(3x-1\right)-\left(5x-2\right)\right]^2=0\)

\(\Leftrightarrow\left(6x-2-5x+2\right)^2=0\)

\(\Leftrightarrow x=0\)

\(\left(2x-5\right)\left(2x+5\right)-1=0\)

\(\Leftrightarrow4x^2-25-1=0\)

\(\Leftrightarrow4x^2-26=0\)

\(\Leftrightarrow4x^2=26\)

\(\Leftrightarrow x^2=\frac{13}{2}\)

\(\Leftrightarrow x=\pm\frac{\sqrt{26}}{2}\)

\(5x^2-20=0\)

\(\Leftrightarrow5x^2=20\)

\(\Leftrightarrow x^2=4\Leftrightarrow x=\pm2\)

Answer 6

\(b,(6x-2)^2+(5x-2)^2-4(3x-1)(5x-2)=0\)

\(\Leftrightarrow36x^2-24x+4+25x^2-20x+4-60x^2-44x+8=0\)

\(\Leftrightarrow(36x^2+25x^2-60x^2)+(24x+20x-44x)+(4+4-8)=0\)

\(\Leftrightarrow x^2=0\Leftrightarrow x=0\)