2^{x+4} – 17 × 2^{x+1} = – 4
2^{x+1} = y
2^{2x+2} = y^{2}
2^{2}(2^{2x+2}) – 17 × 2^{x+1} = –4
4y^{2} – 17y + 4 = 0
4y^{2} – 16y – y + y = 0
4y (y – 4) – 1 (y – 4) = 0
y = or 4
2^{x+1} = or 4
x + 1 = 2 or – 2
x = 1 or – 3
Answer choice (c)
Correct Answer: x can be either a positive value or a negative value