Toán Lớp 8: x^2+ax+3 chia cho x-3 du 3
Tim cac hang so a
Leave a reply
Register Now
Login
Lost Password
Lost your password? Please enter your email address. You will receive a link and will create a new password via email.
Toán Lớp 8: x^2+ax+3 chia cho x-3 du 3
Tim cac hang so a
Comments ( 2 )
{x^2} + a.x + 3\\
= {x^2} – 3x + 3x + a.x + 3\\
= x\left( {x – 3} \right) + \left( {a + 3} \right).x – 3.\left( {a + 3} \right)\\
+ 3.\left( {a + 3} \right) + 3\\
= x\left( {x – 3} \right) + \left( {a + 3} \right).\left( {x – 3} \right) + 3a + 12\\
= \left( {x – 3} \right)\left( {x + a + 3} \right) + 3a + 12\\
Do:\left( {x – 3} \right)\left( {x + a + 3} \right) \vdots \left( {x – 3} \right)\\
\Leftrightarrow 3a + 12 = 3\\
\Leftrightarrow 3a = – 9\\
\Leftrightarrow a = – 3\\
Vậy\,a = – 3
\end{array}$