Question

Vă rog mult!Este urgent!!!​

Answer 1

Explicație pas cu pas:

a)Folosesti formula $(a+b)^{2}$=$a^{2}$+2ab+$b^{2}$

a+b=7⇒$(a+b)^{2}$=49⇒$a^{2}$+$b^{2}$+2ab=49

b)Folosesti formula (a-b)(a+b)=$a^{2}$-$b^{2}$

$a^{2}$-$b^{2}$=28⇒(a-b)(a+b)=28

              4(a+b)=28⇒a+b=7

c)Folosesti formula $(a+b)^{2}$=$a^{2}$+2ab+$b^{2}$

x+1/x=√3⇒$(x+1/x)^{2}$=3⇒$x^{2}$+2x·1/x+1/$x^{2}$=3

$x^{2}$+2+1/$x^{2}$=3

$x^{2}$+1/$x^{2}$=3-2=1