Help plot the following parabola ?

enter image source here

1 Answer
Jun 6, 2018

show below please.

Explanation:

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