Write a quadratic equation for the parabola whose roots are -5/4 and 5.

Question

A. y= 4x² - 15x - 25

B. y= 4x² + 15x +25

C. y= x² - 15x - 25

D. y= x² - 15x + 25

Answer 1

Uruha,

 

Work backwards from the roots.

 

x = -5/4, so x + 5/4 = 0.   Multiply by 4, gives 4x +5 = 0.   4x + 5 is a factor.

 

x = 5, so x - 5 = 0.  x - 5 is a factor.

 

Now we have:

 

y = (4x + 5)(x - 5)

 

or y = 4x² - 15x - 25    (A)