In solving a problem that reduces to a quadratic equation, one student makes a mistake in the constant term and obtains 8 and 2 for roots. Another student makes a mistake only in the coefficient of first-degree term and finds -9 and -1 for roots.
The correct equation is
1
x2 – 10x + 9 = 0
2
x2 + 10x + 9 = 0
3
x2 – 10x + 16 = 0
4
x2 – 8x – 9 = 0