Đáp án + Giải thích các bước giải:
`a)25x²-2=0`
`25x² = 2`
`x² = \frac{2}{25}`
`x = ± \frac{\sqrt{2}}{5}`
b) `x² - 25 = 6x - 9`
x² - 6x - 25 + 9 = 0`
`x² - 6x - 16 = 0`
`x² - 8x + 2x - 16 = 0`
`x(x-8) + 2(x-8) = 0`
`(x-8)(x+2) = 0`
\(\left[ \begin{array}{l}x=8\\x=-2\end{array} \right.\)
c)
`(2x - 10)² - (2x + 5)(2x-5) = 18`
`4x² - 40x + 100 - (4x² - 25) = 18`
`4x² - 40x + 100 - 4x² + 25 = 18`
`-40x + 125 = 18`
`40x = 107`
`x = \frac{107}{40}`
d)
`5x(x-3) - 2x + 6 = 0`
`5x² - 15x - 2x + 6 = 0`
`5x² - 17x + 6 = 0`
`5x² - 2x - 15x + 6 = 0`
`x(5x-2) - 3(5x - 2) = 0`
`(x-3)(5x-2) = 0`
\(\left[ \begin{array}{l}x=3\\x=\dfrac{2}{5}\end{array} \right.\)
