Help plot the following parabola ?

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Answer 1 · 2018-06-06T17:51:43

show below please.

the general quadratic formula is:

#y=ax^2+bx+c#

the vertex of quadratic formula given by:

#x_v=-b/(2a)#

#y_v=a(x_v)^2+b(x_v)+c#

if a positive the shape of sketch will be #uuu#
but if a negative the shape will be #nnn#

now lets sketch #y=-x^2-2x+8#

firstly lets find the vertex:

#x_v=-b/(2a)=2/-2=-1#

#y_v=-1+2+8=9#

#"the vertex"=(-1,9)#

find other points:

#f(2)=0#

#f(1)=5#

#f(0)=8#

#f(-1)=9#

#f(-2)=8#

show below how the sketch will become:

enter image source here