a)9x-18=-63
9x=-63+18
9x=-45
x=-5€Z
b)5x+15=10x-10
15+10=10x-5x
25=5x
x=5€Z
c)8x+2=10x-14
2+14=10x-8x
16=2x
x=8€Z
d)-2x+10=-24x-16+56
24x-2x=40-10
22x=30
x=30/22
x=15/11 nu apartine Z
=> nu are solutii in Z
e)1-4*(-5x+10)=21
1+20x-40=21
20x=21+40-1
20x=60
x=3€Z
f)5x-10-7x-21+35=0
-2x+4=0
-2x=-4
x=2€Z
g)x^2-4x-21=0
delta=16+84
delta=100
=> x1=(4+10)/2=7€Z
x2=(4-10)/2=-3€Z
h)-2x^2+18=0
-x^2+9=0
9-x^2=0
(3-x)(3+x)=0
x1=3€Z
x2=-3€Z