Two equal sides of an isosceles triangle are along -x + 2y = 4 and x + y = 4. If m is the slope of its third side, then the sum of all possible distinct values of m is:
- -2 10
- 12
- -6
- 6
Answer
(4) 6
Solution
Slopes of the equal sides: m1 = 12, m2 = -1
The third side makes equal angles with both equal sides:
| m - 121 + m2 | = | m + 11 - m |
2m - 12 + m = m + 11 - m
(+ sign): (2m - 1)(1 - m) = (m + 1)(m + 2) 3m2 + 3 = 0, no real m
(− sign): (2m - 1)(1 - m) = -(m + 1)(m + 2)
-2m2 + 3m - 1 = -m2 - 3m - 2
m2 - 6m - 1 = 0 m = 3 10 (both real and distinct)
Sum of values of m = 6
Answer: (4)