Question

Tìm nghiệm của các đa thức sau:

a) 3x^2+x-10

b) 2x^2-x-15

c) 7x^2+23x-20

d) 6x^2-35x+25

e) 6x^2-x-2

g) 8x^2+6x-35

Answer 1

3x² + x - 10 = 0

<=> (x + 2)(3x - 5) = 0

\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=\dfrac{5}{3}\end{matrix}\right.\)

2x² - x - 15 = 0

<=> (x - 3)(2x + 5) = 0

\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-\dfrac{5}{2}\end{matrix}\right.\)

7x² + 23x - 20 = 0

<=> (7x - 5)(x + 4) = 0

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{5}{7}\\x=-4\end{matrix}\right.\)

6x² - 35x + 25 = 0

<=> (x - 5)(6x - 5) = 0

\(\Leftrightarrow\left[{}\begin{matrix}x=5\\x=\dfrac{5}{6}\end{matrix}\right.\)

6x² - x - 2 = 0

<=> (3x - 2)(2x + 1) = 0

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{2}{3}\\x=-\dfrac{1}{2}\end{matrix}\right.\)

8x² + 6x - 35 = 0

<=> (4x - 7)(2x + 5) = 0

\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{7}{4}\\x=-\dfrac{5}{2}\end{matrix}\right.\)