Question

Find the coordinates by solving and graphing the equation : -x^2-x+30=0

Answer 1

Diiscriminant :

D = b ^ 2 - 4 a c

in this case :

a = - 1

b = - 1

c = 30


D = ( - 1 ) ^ 2 - 4 * ( - 1 ) * 30

D = 1 + 4 * 30 = 1 + 120 = 121


x1/2 = - b + OR - sqrt ( b ^ 2 - 4 a c ) / 2a

in this case :

x1 = - b + sqrt( b ^ 2 - 4 a c ) / 2a

x1 = [ - ( - 1 ) + sqrt ( 121 ) ] / [ 2 * ( - 1 ) ]

x1 = ( 1 + 11 ) / ( - 2 )

x1 = 12 / - 2

x1 = - 6


x2 = - b - sqrt( b ^ 2 - 4 a c ) / 2a

x2 = [ - ( - 1 ) - sqrt ( 121 ) ] / [ 2 * ( - 1 ) ]

x2 = ( 1 - 11 ) / ( - 2 )

x2 = -10 / - 2

x2 = 5


If you want to see graph in google type:

functions graphs online

When you see results click on :

rechneronline.de/function-graphs/

When page be open in blue rectangle type :

- x ^ 2 - x + 30

Then set :

Range x-axis from - 10 to 10

Range x-axis from - 15 to 35

and click option : Draw

Answer 2

x1/2 = [ - b + OR - sqrt ( b ^ 2 - 4 a c ) ] / 2a