a) 0 (-6-3-2-1+1+2+3+4)
b) este Δechilateral daca are 3 axe de simetrie ⇒ mACB =60
c)( a+b+c)/3 = 310⇒a+b+c=310*3⇒a+b+c=930
a/2=b/3=c/5=(a+b+c)/(2+3+5)=930/10=93⇒a=93*2=186;b=93*3=279;c=93*5=465
d)8x-5x=-5-1⇒3x=-6⇒x=-6/3⇒x=-2
2x-6=x-7⇒2x-x=6-7⇒x=-1
2x-1=5 si 2x-1=-5
2x=5+1 2x=-5+1
2x=6 2x=-4
x=3 x=-2