Bonjour
a. Pour x = - 1
8x² - 3x + 5
= 8 (- 1)² - 3 (- 1) + 5
= 8 (1) + 3 + 5
= 8 + 8
= 16
b. Pour x = 2/3
8x² - 3x + 5
= 8 (2/3)² - 3 (2/3) + 5
= 8 (4/9) - 6/3 + 5
= 32/9 - 18/9 + 45/9
= 59/9
c. Pour x = - 1/4
8x² - 3x + 5
= 8 (- 1/4)² - 3 (- 1/4) + 5
= 8 (1/16) + 3/4 + 5
= 8/16 + 3/4 + 5
= 2/4 + 3/4 + 20/4
= 25/4