2.a=1/(√5-2) +1/(√5+2) aducand la acelasi numitor√⇒
a=(√5+2+√5-2)/(5-4)=2√5 =4,72
2√5∈(√19,√21) daca faciradicali vei vedea
3. f(x)+4≤f(2x) (vezi ca nu am la taste doar mai mic deci nu este si egal ci MAI MIC)
f(x)=3-2x
3-2x+4≤3-4x
-2x≥0
x mai mare ca zero x∈(0.+∞)
4.V=lxLxh=2x3x100=600m³ de beton
6.a/2=b/5=k
a=2k
b=5k
a=p/100b
2k=5k.p/100⇒p=40
7.a) P(1)=1-4+a+b=-3
P(-1)=-1-4-a+b=7
sistem
a+b=o
-a+b=12
2b=12
b=6
a=-6
P(x)=x³-4x²-6x+6
b)P(x)+9x-6=x³-4x²-6x+6-6x+6=x³-4x²-12x+12=x²(X-1) -12(x-1)=(x-1)(x²-12)=(x-1)(x-2√3)(x+2√3)
5.asta daca recipientul rae si capac
At=16x16x2 +16x30x4+15x15x2 +15x25x4=4382 interior si exterior
daca nu are capac trebuie scazut 16x16+15x15
V=16x16x30-15x15x25=2055 cm³
G=2055x2,7=5548.5g