1)=4laput.48(4²+4+1) div 21
=4la put.48·21 div cu 21
=(2²)laput.48·21div cu 21 este patrat perfect
3) 3la put.(2x+4)+3la put.(2x+2)+3la put.2x=91·3la put.28
3la put2x·3la put.4+3la put.2x·3²+3la put.2x=91·3la put.28
3la put.2x(81+9+1)=91·3laput.28
3la put.2x·91=91·3 la put.28
not.3·91=t
t la put.2x=tla put.28
2x=28
x=28/2
x=14