GraPH THE QUADRATIC function label the vertex axis of symmetry and x intercepts also domain and range

y=3x^2+21x+36
Graph included

Question

GraPH THE QUADRATIC function label the vertex axis of symmetry and x intercepts also domain and range 

y=3x^2+21x+36
Graph included

campbell_st · Answer

take 3 out as a common factor

y =3(x^2 + 7x + 12)

factorise the quadratic 

0 = 3(x+3)(x+4)

so the intercepts:  y intercept   (x = 0) is  36

x intercepts     (y = 0)     x = -4, -3

axis of symmetry is     x = -b/2a    x = -21/6          x = -3.5

the axis if symmetry is x = -3.5

substitute it into the equation to find the vertex

y = 3(-3.5)^2 + 21(-3.5) + 36

y = -0.75

vertex (-3.5, -0.75)

domain is all real x

range y >= -0.75

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