Cho ba vectơ a = (2; 1), b = (3; 4), c = (7; 2) Giá trị của k; h c = ka + hb

* Hướng dẫn giải

$\left.\begin{array}{l}k.\overrightarrow{a}=\left(2k;k\right)\\ h.\overrightarrow{b}=\left(3h;4h\right)\end{array}\right\}\Rightarrow k.\overrightarrow{a}+h.\overrightarrow{b}=\left(2k+3h;k+4h\right).$

$\overrightarrow{c}=k.\overrightarrow{a}+h.\overrightarrow{b}\iff \left\{\begin{array}{l}7=2k+3h\\ 2=k+4h\end{array}\right.\iff \left\{\begin{array}{l}k=\mathrm{4,4}\\ h=-\mathrm{0,6}\end{array}\right..$

Đáp án C