Question

1.Aflati nr intreg pt care (3x+1)^2=4
2.Pretul unui telefon mobil creste cu 10% apoi scade cu 15% ajungand sa coteste 561 lei . aflati pretul initial al tel.

Answer 1

[tex]1. (3x+1)^2=4\\ 9x^2+6x+1=4\\ 9x^2+6x-3=0\\ 3x^2+2x-1=0\\ 3x^2+3x-x-1=0\\ 3x(x+1)-(x+1)=0\\ (3x-1)(x+1)=0\\ i)3x-1=0\Rightarrow x=\frac{1}{3} \notin Z\\ ii)x+1=0\Rightarrow x=-1 \in Z[/tex]
[tex]2.x=pretul\ initial\\ x+\frac{10}{100}*x-\frac{15}{100}(x+\frac{10}{100}*x})=561\\ \frac{110x}{100}-\frac{15}{100}\cdot \frac{110x}{100}=561\\ \frac{110x}{100}-\frac{1650x}{10000}=561|\cdot 10000\\ 11000x-1650x=5610000\\ 9350x=5610000\\ x=600 lei[/tex]