13.
3 - 2x = 11 ⇒ 3 - 11 = 2x ⇒ -8 = 2x ⇒ x= - 8:2⇒ x = - 4
14.
6 robinete..............................2 ore (120 min)
4 robinete..............................x ore (...min)
x= (4×120)/6
x= 480/6
x= 80 min ( 1h si 20 min)
15.
Aria rombului cand se cunosc diagonalele= semiprodusul diagonalelor
A=(15 ×11):2=82,5 cm²
16.
mg=√9×16=√144 = 12
17.[tex] aria=\frac{a^{2}\sqrt{3}}{4} [/tex]
[tex] aria=\frac{a^{2}\sqrt{3}}{4} =\frac{36\sqrt{3}}{4}=9\sqrt{3} [/tex]
18.
2x-3<5 ⇒ 2x < 5 + 3⇒ 2x < 8 ; x < 8/2 ; x < 4
deci x∈ (-∞,4)
19. latura = 3 cm
Perimetrul = 4 × 3 = 12 cm
20.
x = (√3 -1 )²+2√3 = 3 -2√3 +1 + 2√3 = 4
y = (√5-2)(√5+2)+2016° iar 2016° = 1
y = (√5)² -2²= 5 - 4 + 1 = 2
Ma = (x + y)/2 = (4 +2 ) / 2 = 6/2 = 3
