00:01
So i have f of x equals x squared plus b times x minus 25, and the minimal value is minus 50.
00:09
So now i want to find value of b such that the function has a given minimum value of minus 50.
00:25
So i know this function a is equals 1, which is greater than 0.
00:30
So which means the graph of this function is concave up like this.
00:34
So the function has a minimum value point.
00:36
Now, what is x coordinate of the minimum value point? it is 1x equals minus b over 2a.
00:46
Half of x will reach the minimum point, which is 4 times a times c minus b squared, divided by 4 times a.
00:55
Okay? so 1x equals minus b over 2a, which is 2 times 1, which is minus b over 2a, which is minus b over 2a, which is minus b over 2, 2...