Question

Determine o ccalor de X para que os pontos A(2,-3), B (x,7)e C (x,1) sejam colineares

Answer 1

Resolva o determinante e iguale a zero;

$\\ det \left[\begin{array}{ccc}2&-3&1\\x&7&1\\x&1&1\end{array}\right] =0 \\ \\ 2*7*1-3*1*x+x*1*1-(x*7*1+1*1*2+-3*x*1)=0 \\ \\ 14-3x+x-(7x+2-3x)=0 \\ \\ -3x+x-7x+3x+14-2=0 \\ \\ -6x+12=0 \\ \\ 6x=12 \\ \\ x = \frac{12}{6} \\ \\ x=2$