Explicație pas cu pas:
1. 2/3√7+10/21=2√7/21+10/21=2√7+10/21=2(√7+5)/21.
2.x²-3x+2=x²-x-2x+2=x(x-1)-2(x-1)=(x-2)•(x-1)
3. 9/3x+11=3/11=>3(3x+1)=11×9=99=>9x+3=99=>9x=99-3=96=>x=96/9=23/3=7,(6)=>x=7,(6).
4. ∆ABC dr in A(conform teoremei lui Pitagora)=>BC²=AB²+AC²=3²+4²=9+16=25=>BC²=25=√25=5=>BC=5cm(ipotenuza).
