Question

10 +20 +30....+X0=360

Answer 1

[tex]10+20+30+.....+10x=360\\ 10(1+2+3+...+x)=360\\ 1+2+3+...+x=36\\ \frac{x(x+1)}{2}=36\\ x^2+x=72\\ x^2+x-72=0\\ x^2+9x-8x-72=0\\ x(x+9)-8(x+9)=0\\ (x+9)(x-8)=0=\ \textgreater \ x_1=-9(nu\ apartine\ lui\ N),x_2=8\\ Deci\ x=8 [/tex]