Bonsoir,
W = 7 * ( x + 2x²) - 3 (5-x) + 2x (x² -4)
7*x = 7x
7* 2x² = 14x²
-3*5 = -15
-3* -x = 3x
2x*x² = 2x³
2x*-4 = -8x
=>
7x +14x²-15 +3x +2³-8x
= 2x³ +14x²+2x -15
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Z = -2 * (π+4) - 2π (5-R) - 12 (-1 -π)
-2*π =-2π
-2*4 = -8
-2π*5 = 10π
-2π *-R = 2πR
-12*-1 = 12
-12*- π =12π
=>
-2 π -8+10π +2πR +12+12π
=2πR +22π +4