a-12=0 (a+b-3)^2=0 a= b= At ten o'clock, the angle between the hour hand and the minute hand is () ° If a + b > 0 AB is known, the symbols of a and B are A is 15 years older than B. five years ago, a was twice as old as B. B is now 15 years old If each inner angle of a convex polygon is 140 degrees, then there are several diagonals starting from a vertex of the polygon

a-12=0 (a+b-3)^2=0 a= b= At ten o'clock, the angle between the hour hand and the minute hand is () ° If a + b > 0 AB is known, the symbols of a and B are A is 15 years older than B. five years ago, a was twice as old as B. B is now 15 years old If each inner angle of a convex polygon is 140 degrees, then there are several diagonals starting from a vertex of the polygon

1)a=12,b=-9
2)60
3) The sign of a is positive and the sign of B is negative
4）20
5）（n-2）*180
Because each angle is 140 degrees
140x=180x-360
x=9
It is a nine sided shape
Starting from a vertex, there can be (x-3), that is, 6