Đáp án:
B1:
a) k=1
Giải thích các bước giải:
\(\begin{array}{l}
B1:\\
a)Thay:x = - 2\\
Pt \to 2\left( { - 2} \right) + k = - 2 - 1\\
\to k = 1\\
b)Thay:x = 2\\
Pt \to \left( {2.2 + 1} \right)\left( {9.2 + 2k} \right) - 5\left( {2 + 2} \right) = 40\\
\to 5\left( {2k + 18} \right) - 20 = 40\\
\to 2k + 18 = 12\\
\to 2k = - 6\\
\to k = - 3\\
c)Thay:x = 1\\
Pt \to 2\left( {2.1 + 1} \right) + 18 = 3\left( {1 + 2} \right)\left( {2.1 + k} \right)\\
\to 2.3 + 18 = 3.3\left( {2 + k} \right)\\
\to k + 2 = \dfrac{8}{3}\\
\to k = \dfrac{2}{3}\\
d)Thay:x = 2\\
Pt \to \left( {5m + 3.2} \right)\left( {2 + 1} \right) - 4\left( {1 + 2.2} \right) = 80\\
\to \left( {5m + 6} \right).3 - 20 = 80\\
\to 5m + 6 = \dfrac{{100}}{3}\\
\to m = \dfrac{{82}}{{15}}\\
B2:\\
a)\left( {x - 1} \right)\left( {2x - 1} \right) = 0\\
\to \left[ \begin{array}{l}
x = 1\\
x = \dfrac{1}{2}
\end{array} \right.\\
Thay:\left[ \begin{array}{l}
x = 1\\
x = \dfrac{1}{2}
\end{array} \right.\\
Pt \to \left[ \begin{array}{l}
m{.1^2} - \left( {m + 1} \right).1 + 1 = 0\\
m.{\left( {\dfrac{1}{2}} \right)^2} - \dfrac{1}{2}\left( {m + 1} \right) + 1 = 0
\end{array} \right.\\
\to \left[ \begin{array}{l}
m - m - 1 + 1 = 0\\
\dfrac{1}{4}m - \dfrac{1}{2}m - \dfrac{1}{2} + 1 = 0
\end{array} \right.\\
\to \left[ \begin{array}{l}
0 = 0\left( {ld} \right)\\
- \dfrac{1}{2}m + \dfrac{1}{2} = 0
\end{array} \right.\\
\to m = 1\\
b)\left( {x - 3} \right)\left( {ax + 2} \right) = 0\\
\to \left[ \begin{array}{l}
x = 3\\
x = - \dfrac{2}{a}\left( {a \ne 0} \right)
\end{array} \right.\\
Thay:\left[ \begin{array}{l}
x = 3\\
x = - \dfrac{2}{a}\left( {a \ne 0} \right)
\end{array} \right.\\
Pt \to \left[ \begin{array}{l}
\left( {2.3 + b} \right)\left( {3 + 1} \right) = 0\\
\left( {2.\left( { - \dfrac{2}{a}} \right) + b} \right)\left( { - \dfrac{2}{a} + 1} \right) = 0
\end{array} \right.\\
\to \left[ \begin{array}{l}
b = - 6\\
b - \dfrac{4}{a} = 0\\
- \dfrac{2}{a} + 1 = 0
\end{array} \right.\\
\to \left[ \begin{array}{l}
b = - 6\\
b = \dfrac{4}{a}\\
a = 2
\end{array} \right.
\end{array}\)
