Question

(x+1)*(x+2)=72

stiu ca x=7 dar cum se rezolva ?

Answer 1

(x+1)*(x+2)=$x^{2}$+3x+2
$x^{2}$+3x+2-72=0 (ecuatie de gradul II)
a=1,b=3,c=-70
Δ=delta
Δ=$b^{2}$-4ac
  =9-(-280)
  =289 (ecuatia are doua solutii reale)
x1=$\frac{-b+\sqrt{delta}}{2a}$
x1=7
x2=$\frac{-b-\sqrt{delta}}{2a}$
x2=-10