(2x-1)^2-(x+2)^2=25
ai formulele:
(a+b)^2=a^2+2ab+b^2
(a-b)^2=a^2-2ab+b^2
4x^2-4x+1-(x^2+4x+4)=25
4x^2-4x+1-x^2-4x-4=25
3x^2-8x-3=25
3x^2-8x-28=0
a=3
b= -8
c= -28
delta=b^2-4ac
=64 - 4 ori 3 ori (-28)
=64 - 12 ori (-28)
=64 + 336
=400
notam radical din delta cu d ==> d= radical din 400 = 20
x1 = (-b-d)/2a = (8-20)/6 = -12/6 = -2
x2 = (-b+d)/2a = (8+20)/6 = 28/6 = 14/3
