5.若线性方程组的增广矩阵为 $\left(\begin{array}{lll}2 & 3 & c_{1} \\ 0 & 1 & c_{2}\end{array}\right)$ 解为 $\left\{\begin{array}{l}x=3 \\ y=5\end{array}\right.$ ,则 $c_{1}-c_{2}=$
参考答案16
2015_上海卷 (2015·文)
5.若线性方程组的增广矩阵为 $\left(\begin{array}{lll}2 & 3 & c_{1} \\ 0 & 1 & c_{2}\end{array}\right)$ 解为 $\left\{\begin{array}{l}x=3 \\ y=5\end{array}\right.$ ,则 $c_{1}-c_{2}=$
【答案】 16
【解析】由题意,$\left\{\begin{array}{l}x=3 \\ y=5\end{array}\right.$ 是方程组 $\left\{\begin{array}{l}2 x+3 y=c_{1} \\ y=c_{2}\end{array}\right.$ 的解,所以 $\left\{\begin{array}{l}c_{1}=21 \\ c_{2}=5\end{array}\right.$ ,所以 $c_{1}-c_{2}=21-5=16$.
【考点定位】增广矩阵,线性方程组的解法.