1013 Найдите координаты вектора и, если: а) = 34-36, a {2; -5), 6(-5; 2); 6) = 2a-36+4c, a {4; 1), 6 {1; 2), (2; 7}; B) =30-26-2, 6-7;-1), 6 (-1; 7}, {4;-6); r) =a-b-c, a (7; -2), 6 (2; 5), c{-3; 3).

a) $$\overrightarrow{u} = 3\overrightarrow{a} - 3\overrightarrow{b}$$, $$\overrightarrow{a}(2; -5)$$, $$\overrightarrow{b}(-5; 2)$$.

$$3\overrightarrow{a} = (3 \cdot 2; 3 \cdot (-5)) = (6; -15)$$.

$$3\overrightarrow{b} = (3 \cdot (-5); 3 \cdot 2) = (-15; 6)$$.

$$\overrightarrow{u} = (6 - (-15); -15 - 6) = (21; -21)$$.

б) $$\overrightarrow{u} = 2\overrightarrow{a} - 3\overrightarrow{b} + 4\overrightarrow{c}$$, $$\overrightarrow{a}(4; 1)$$, $$\overrightarrow{b}(1; 2)$$, $$\overrightarrow{c}(2; 7)$$.

$$2\overrightarrow{a} = (2 \cdot 4; 2 \cdot 1) = (8; 2)$$.

$$3\overrightarrow{b} = (3 \cdot 1; 3 \cdot 2) = (3; 6)$$.

$$4\overrightarrow{c} = (4 \cdot 2; 4 \cdot 7) = (8; 28)$$.

$$\overrightarrow{u} = (8 - 3 + 8; 2 - 6 + 28) = (13; 24)$$.

в) $$\overrightarrow{u} = 3\overrightarrow{a} - 2\overrightarrow{b} - \frac{1}{2}\overrightarrow{c}$$, $$\overrightarrow{a}(-7; -1)$$, $$\overrightarrow{b}(-1; 7)$$, $$\overrightarrow{c}(4; -6)$$.

$$3\overrightarrow{a} = (3 \cdot (-7); 3 \cdot (-1)) = (-21; -3)$$.

$$2\overrightarrow{b} = (2 \cdot (-1); 2 \cdot 7) = (-2; 14)$$.

$$\frac{1}{2}\overrightarrow{c} = (\frac{1}{2} \cdot 4; \frac{1}{2} \cdot (-6)) = (2; -3)$$.

$$\overrightarrow{u} = (-21 - (-2) - 2; -3 - 14 - (-3)) = (-21; -14)$$.

г) $$\overrightarrow{u} = \overrightarrow{a} - \overrightarrow{b} - \overrightarrow{c}$$, $$\overrightarrow{a}(7; -2)$$, $$\overrightarrow{b}(2; 5)$$, $$\overrightarrow{c}(-3; 3)$$.

$$\overrightarrow{u} = (7 - 2 - (-3); -2 - 5 - 3) = (8; -10)$$.

Ответ: а) (21; -21); б) (13; 24); в) (-21; -14); г) (8; -10).