# Decide 2

Decide whether points A[-2, -5], B[4, 3] and C[16, -1] lie on the same line

Correct result:

x =  0

#### Solution:

$u=(4-(-2), 3-(-5))=(6, 8) \ \\ v=(16-(-2), -1 -(-5))=(18, 4) \ \\ \ \\ s=u \cdot \ v=|u||v| \cos α \ \\ \ \\ \cos α=c \ \\ \ \\ c=\dfrac{ 6 \cdot \ 18+8 \cdot \ 4 }{ \sqrt{ 6^2+8^2 } \cdot \ \sqrt{ 18^2+4^2 } } \doteq 0.7593 \ \\ \ \\ c \ne 0 \ \\ \ \\ x=0$

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Ziacka
don't lie on same line

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