Question

Calcule o valor de a sabendo que a distância entre A( 2, a ) e B( 1, -4 ) é igual a 1.

Answer 1

$d_{AB}=1\\\\\sqrt{(1-2)^2+(-4-a)^2}=1\\\\(\sqrt{1+16+8a+a^2})^2=(1)^2\\\\a^2+8a+17=1\\\\a^2+8a+16=0\\\\(a+4)^2=0\\\\\boxed{a=-4}$