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#29946

systems

equations

slopes

lines

coordinate geometry

geometry

algebra

hard

100 sec

Calculator OK

Lines $L_{1}$ and $L_{2}$ are perpendicular in the $x y$ -plane. Line $L_{1}$ has the equation $A_{1} x + B_{1} y = C_{1}$ , and line $L_{2}$ has the equation $A_{2} x + B_{2} y = C_{2}$ , where $A_{1}, B_{1}, C_{1}, A_{2}, B_{2}, C_{2}$ are constants and $B_{1} \neq = 0, B_{2} \neq = 0$ . Which of the following must be true?

A.

$A_{1} A_{2} - B_{1} B_{2} = 0$

B.

$A_{1} B_{2} + A_{2} B_{1} = 0$

C.

$A_{1} A_{2} + B_{1} B_{2} = 0$

D.

$A_{1} B_{1} + A_{2} B_{2} = 0$