Question

cho a + b = 4 ; a.b = 3. hãy tính a - b

giúp nhé!!

Answer 1

\(a+b=4\)

\(\Rightarrow\left(a+b\right)^2=4^2=16\)

\(\Rightarrow a^2+b^2+2ab=16\)

\(\Rightarrow a^2+b^2+2.3=16\)

\(\Rightarrow a^2+b^2=16-6=10\)

\(\Rightarrow a^2+b^2-2ab=10-6=4\)

\(\Rightarrow\left(a-b\right)^2=4\)

\(\Rightarrow a-b\in\left\{2;-2\right\}\)

Answer 2

\(\left(a+b\right)^2=4^2=16\)

\(=>a^2+2ab+b^2=16\)

\(=>a^2+b^2+6=16\)

\(=>a^2+b^2=10\)

Ta có \(a^2-2ab+b^2=10-2.3\)

\(=10-6=4\)

\(=>a^2-2ab+b^2=\left(a-b\right)^2=4\)

\(=>a-b=\sqrt{4}=2\)

Vậy a - b = 2 

Ủng hộ nha

Answer 3

Ta có: \(\left(a-b\right)^2=a^2-2ab+b^2=a^2+2ab+b^2-4ab=\left(a+b\right)^2-4ab\)

\(=4^2-4.3=4=>a-b=2\)