Quadratic Functions.............................

Question

Evaluate given quadratic functions

 

(1)f(x)=x^2+8x+6, Find f(-5)

 

(2)g(x)=5x^2-4x+8, g(-9)

 

(3) f(x)=x^2+2x-17, f(a-4)

 

Find all fixed points for the following functions by setting the function equal to x and solving the resulting equation for x

 

(1) f(x)=x^2-5x+8

 

 

Answer 1

1.   (-5)² + 8(-5) + 6 = 25 - 40 + 6 = -9

 

2.  5(-9)² - 4(-9) + 8 = 5(81) + 36 + 8 = 405 + 36 + 8 = 449

 

3.  (a-4)² + 2(a-4) - 17   =   a² - 8a + 16 + 2a - 8 - 17 = a² - 6a - 9 = (a-3)²

 

 

 

Going by the directions on that last one...

x = x² - 5x + 8

 

0 = x2 - 6x + 8

 

0 = (x-4)(x-2)

 

x={2, 4}