Question

Aflati valoarea numărului natural X, stiind că:
(X+1)×(X+2)=56

Answer 1

(X+1)×(X+2)=56
X×X+X×2+1×X+1×2=56
X²+2X+X+2=56
X²+3X+2-56=0
X²+3X-54=0
a=1
b=3
c=-54
∆=b²-4ac
∆=3²-4×1×(-54)
∆=9+216
∆=225
X(1,2)=(-b±√∆)/2a
X(1,2)=(-3±√225)/(2×1)
X(1,2)=(-3±15)/2
X(1)=(-3+15)/2
X(1)=12/2
X(1)=6
X(2)=(-3-15)/2
X(2)=-18/2
X(2)=-9

Answer 2

(X+1)×(X+2)=56

stim ca 7×8=56

x+1=7
x=7-1
x=6

x+2=8
x=8-2
x=6

verificare:
(6+1)×(6+2)=7×8=56