the given expression is,
[tex]y=x^2-10x+21[/tex]
the standard equation is y = ax^2 + bx +c
it is a quadratic equation, so the x coordinate of the vertex of this equation is,
= -b/2a
so, the x coordinate is,
= -(-10)/2(1)
= 10/2
= 5
put x = 5 in the above equation,
y = 5^2 - 10(5) + 21
y = 25 - 50 + 21
y = 46 - 50
y = -4
so the vertex is (5, -4) that is option B
