Sagot :
a)
3(2x-6)-(3-5x)
3*2x+3*(-6)-(3-5x)
6x-18-3+5x
11x-21
b)
(5-2y)-(-3y+7)
5-2y+3y-7
y-2
c)
4(6+z)+(z-3)(2-z)
4*6+4*z+z*2+z*(-z)-3*2-3*(-z)
24+4z+2z-z²-6+3z
-z²+9z+18
d)
(2t-5)(3t+2)-(t²+6)
2t*3t+2t*2-5*3t-5*2-t²-6
6t²+4t-15t-10-t²-6
5t²-11t-16
a) 3(2x - 6) - (3 - 5x )
= 6x - 18 - 3 + 5x
= 11x - 21
b) (5 - 2y) - (-3y + 7)
= 5 - 2y + 3y - 7
= y - 2
c) 4(6+z) + (z-3) (2-z)
= 24 + 4z + 2z - z² - 6 + 3z
= -z² + 9z + 18
d) (2t-5) (3t+2) - (t²+6)
= 6t² + 4t - 15t - 10 - t² - 6
= 5t² -11t - 16
voilà ! :)