7)a) 13*13=x*x=>169=x^2 => x=13
b)4*20=5x*x=> x^2=80/5=16=> x=4
c)3+x*3-x=8 => 9+x^2=8 => x^2=9-8=1 => x=1
d)3x*3x=4=> 9*x^2=4=> x^2=9/4=2,25 => x=1,5
e)x+1*x+1=8*2=16 => x^2+1= 16=> x^2=15=> x=3,8
f)x^2+10*6=12*5=> x^2=60/60=> x=1
Sper ca te-am ajutat ;) !
