If (α,β) is the orthocentre of the triangle ABC with vertices A(3,−7),B(−1,2) and C(4,5), then 9α−6β+60 is equal to:
(A)30
(B)25✓ Correct
(C)40
(D)35
Answer: (B)
Solution
The orthocentre is the intersection of two altitudes. The slope of BC is 4−(−1)5−2=53, so the altitude from A(3,−7) has slope −35, giving 5x+3y+6=0. The slope of AC is 4−35−(−7)=12, so the altitude from B(−1,2) has slope −121, giving x+12y=23. Solving these, α=−1947 and β=57121. Hence 9α−6β+60=9(−1947)−6(57121)+60=25.
JEE Main · 2023 · 15 Apr 2023 · Shift 1 · Single correct option