(30a = (1,3), 6 =(2, 1) のとき、a+tb=5√2 となる実数tの値を求めよ。
a + tb² = (1, 3) + t (2, 1)
3 = (1 + 2 + 3 + t )
lãi thp = (55)2
(1 + 2)² + (3 + 1)² = 50
4 t +1
t² + 2t - 8 = 0
(t14) (t-2) = 0 F 1)
t = -4.2
4t² +4 t +1+t² + 6 + 9 = 50
5t² + lot -40 =50
5(t² 12t-8) -50