#"the equation of a parabola in "color(blue)"vertex form "#is.

#color(red)(bar(ul(|color(white)(2/2)color(black)(y=a(x-h)^2+k)color(white)(2/2)|)))#

where ( h , k ) are the coordinates of the vertex and a is a constant.

#y-4=-(x-1)^2#

#"add 4 to both sides"#

#ycancel(-4)cancel(+4)=-(x-1)^2+4#

#rArry=-(x-1)^2+4larrcolor(red)" in vertex form"#

#"with " h=1" and " k=4#

#rArrcolor(magenta)"vertex "=(1,4)#

#color(blue)"Intercepts"#

#• " let x = 0, in equation for y-intercept"#

#• " let y = 0, in equation for x-intercepts"#

#x=0toy=-(0-1)^2+4=3larrcolor(red)" y- intercept"#

#y=0to-(x-1)^2+4=0#

#rArr-(x-1)^2=-4#

#"multiply both sides by - 1"#

#rArr(x-1)^2=4#

#color(blue)"take the square root of both sides"#

#sqrt((x-1)^2)=+-sqrt4larrcolor(red)" note plus or minus"#

#rArrx-1=+-2larr" add 1 to both sides"#

#rArrx=1+-2#

#rArrx=1-2=-1,x=1+2=3larrcolor(red)" x- intercepts"#

graph{-(x-1)^2+4 [-10, 10, -5, 5]}