y = - (x - 5)² + 4
the equation of a quadratic in standard form is
y = a(x - h)² + k ( where (h , k ) are the coordinates of the vertex and a is a multiplier )
given vertex = ( 5, 4 ) then
y = a(x - 5)² + 4 ( to find a substitute (7 , 1 ) into the equation )
1= 4a + 4
4a = - 3 ⇒ a = -
y = - (x - 5)² + 4 ← ( in vertex form )