Vă rog mult!Este urgent!!!

Explicație pas cu pas:
a)Folosesti formula [tex](a+b)^{2}[/tex]=[tex]a^{2}[/tex]+2ab+[tex]b^{2}[/tex]
a+b=7⇒[tex](a+b)^{2}[/tex]=49⇒[tex]a^{2}[/tex]+[tex]b^{2}[/tex]+2ab=49
b)Folosesti formula (a-b)(a+b)=[tex]a^{2}[/tex]-[tex]b^{2}[/tex]
[tex]a^{2}[/tex]-[tex]b^{2}[/tex]=28⇒(a-b)(a+b)=28
4(a+b)=28⇒a+b=7
c)Folosesti formula [tex](a+b)^{2}[/tex]=[tex]a^{2}[/tex]+2ab+[tex]b^{2}[/tex]
x+1/x=√3⇒[tex](x+1/x)^{2}[/tex]=3⇒[tex]x^{2}[/tex]+2x·1/x+1/[tex]x^{2}[/tex]=3
[tex]x^{2}[/tex]+2+1/[tex]x^{2}[/tex]=3
[tex]x^{2}[/tex]+1/[tex]x^{2}[/tex]=3-2=1