On donne 5xpetit2-7x+1. calculé c pour:a)x=-1. b)x=3. c)x=2sur5

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5 x² - 7 x +1

pour  x = -1

5 - 7 +1 = - 1

pour x = 3

45 - 21 + 1 = 25

pour x = 2/5
20/25 - 14/5 + 1
20/25 - 70/25 + 25/25 = - 25/25 = - 1

5x²-7x +1

pour:a)x=-1
5 X (-1)² - [7 X (-1)] +1
= 5 + 7 +1
= 13

b)x=3.
5 X 3² -7 X3 + 1
= 5 X 9 -21 +1
= 45 -20
= 25

c)x=2sur5
5 X (2/5)² - 7 X (2/5) +1
= 5 X(4/25) -14/5 + 1
= 20/25 -14/5 = 5/5
= 4/5 -14/5 +5/5
=-5/5
=-1