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Sonia graphs the equations y = –x2 + 4x and y = x – 4 to solve the equation –x2 + 4x = x – 4. Her graph is shown below. What are the solutions of –x2 + 4x = x – 4? A.–5 and 0
B.–5 and –1
C.–1 and 4
D.0 and 4

Respuesta :

C -1 and 4 i just did the test on this
smmwaite

Answer

C.–1 and 4


Explanation

Solving the equations  y = –x² + 4x and y = x – 4

–x² + 4x = x – 4

x² - 4x + x = 4

x² - 3x = 4

x² - 3x + (3/2)² = 4 +  (3/2)²

(x - 3/2)² = 4 +  9/4

              = 6.25

x - 3/2 = √6.25                      or  x - 3/2 = -√6.25

x = 2.5 + 1.5                                        x = -2.5 + 1.5

 = 4                                                        = -1


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