P=2l+2L= 2(L-7) +2L= 2L -14 +2L = 4L -14
2) (√3-1)/√3 + (√5-√3)/√15 -(√7-√5)/√35 + (√9-√7)/√63 rationalizam
(3-√3)/3 +(5√3 -3√5)/15 - (7√5 -5√7)/35 + (9√7 -7*3)/63 aducem la acelasi numitor
2205 +735√3 -735√3 - 441√5 + 441√5 -315√7 +315√7 -735=
=2205 -735=
=1470
3)13*4=52
52-13=39 anii peste care va avea 52 de ani
4)(√900:√50)² - (90-2√3600+40)=
=(√18)² -(130 -2*60)=
= 18 - (130-120)=
=18 -10=8
