How do you graph y = 2x^ 2-13x-7?

1 Answer
Feb 20, 2018

See below for a full explanation:

Explanation:

You can find the "zeroes (x-intercepts), y-intercepts, and the vertex."

The standard form of a quadratic equation is

ax^2+bx+c

with c being the "y-intercept".

The "y-intercept" of this equation is -7 as c is -7.

To find the "zeroes", plug 0 for y. Use the quadratic formula.

(-b+-sqrt(b^2-4ac))/(2a)

Identify a,b,"and" c:

a=2

b=-13

c=-7

Plug in:

(-(-13)+-sqrt((-13)^2-4*2*-7))/(2*2)=>

(13+-sqrt(225))/4=>

(13+-15)/4

The zeroes are

7,-1/2

This was also factorable, as a discriminant (b^2-4ac) that is a perfect square tells us that the equation is factorable (225 is a perfect square).

You could factor and get

(2x+1)(x-7)=>

x=7,-1/2

To get the vertex of an equation ax^2+bx+c, use:

h=(-b)/(2a)

k=c-(b^2)/4a

with (h,k) being the vertex:

a=2

b=-13

c=-7

h=(-(-13))/(2*2)=>13/4

k=-7-((-13)^2)/(4*2)=>-56/8-169/8=>-225/8

The vertex is (13/4,-225/8)

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Summary:

"y-intercept":(0,7)

"x-intercepts": (7,0) and (-1/2,0)

"vertex":(13/4,-225/8)