If two lines are parallel, what must be true about their slopes (m1m_1m1 and m2m_2m2)?
m1=m2m_1 = m_2m1=m2
m1⋅m2=−1m_1 \cdot m_2 = -1m1⋅m2=−1
m1+m2=0m_1 + m_2 = 0m1+m2=0
m1=−m2m_1 = -m_2m1=−m2