Câu 1:
a: \(A=\left(2+\sqrt{3}\right)\left(2-\sqrt{3}\right)=1\)
b: \(B=\left(\dfrac{\sqrt{b}}{\sqrt{a}\left(\sqrt{a}-\sqrt{b}\right)}-\dfrac{\sqrt{a}}{\sqrt{b}\left(\sqrt{a}-\sqrt{b}\right)}\right)\cdot\left(a\sqrt{b}-b\sqrt{a}\right)\)
\(=\dfrac{b-a}{\sqrt{ab}\left(\sqrt{a}-\sqrt{b}\right)}\cdot\sqrt{ab}\left(\sqrt{a}-\sqrt{b}\right)=b-a\)
Câu 2:
b: \(P=\left(x_1+x_2\right)^2-2x_1x_2=1^2-2\cdot\left(-3\right)=1+6=7\)
Đúng 1
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