Bonsoir,
1a. Vicor choisit 10 : 10 + 5 = 15; 15 × 10 = 150 ; 150 - 10 = 140 ; 140 - 10 = 130.
1b.
[tex]f(x) = 10(x + 5) - x - 10 \\ f(x) = 10x + 50 - x - 10 \\ f(x) = 9x + 40[/tex]
2a.
[tex]9x + 40 = 238 \\ 9x = 198 \\ x = 22[/tex]
2b.
[tex]f( x) = \frac{(x - 40)}{9} [/tex]