Homework Help

How do I determine the x-intercepts of f(x) = -5x² + 20x + 2?

user profile pic

m1k3y | Student, Grade 11 | (Level 1) eNoter

Posted August 25, 2012 at 3:09 PM via web

dislike 4 like

How do I determine the x-intercepts of f(x) = -5x² + 20x + 2?

2 Answers | Add Yours

Top Answer

user profile pic

mjripalda | High School Teacher | (Level 1) Senior Educator

Posted August 25, 2012 at 3:36 PM (Answer #1)

dislike 3 like

`f(x)=-5x^2+20x+2`

To determine x-intercept, set f(x)=0.

`0=-5x^2+20x+2`

Then, use the quadratic formula to solve for x.

`x=[-b+-sqrt(b^2-4ac)]/(2a)= [-20+-sqrt((-20)^2-4(-5)(2))]/((-5)(2))= (-20+-2sqrt110)/(-10)`

`x_1= 2+sqrt110/5`                and               `x_2=2-sqrt110/5`

Hence, the x-intercepts of `f(x)=-5x^2+20x+2` are `(2+sqrt110/5,0)` and `(2-sqrt110/5, 0)` .

Sources:

Top Answer

user profile pic

sodapopjo | Student, Grade 11 | (Level 1) Honors

Posted August 25, 2012 at 3:45 PM (Answer #2)

dislike 1 like

(2 + √110/5, 0) and (2 - √110/5, 0)

Join to answer this question

Join a community of thousands of dedicated teachers and students.

Join eNotes