Đáp án:
Giải thích các bước giải:
a) `\frac{\sqrt{5}+3}{\sqrt{5}-3}+\frac{\sqrt{5}-3}{\sqrt{5}+3}=-7`
`VT=\frac{\sqrt{5}+3}{\sqrt{5}-3}+\frac{\sqrt{5}-3}{\sqrt{5}+3}`
`VT=\frac{(\sqrt{5}+3)^2}{(\sqrt{5}-3).(\sqrt{5}+3)}+\frac{(\sqrt{5}-3)^2}{(\sqrt{5}-3).(\sqrt{5}+3)}`
`VT=\frac{14+6\sqrt{5}+14-6\sqrt{5}}{-4}`
`VT=\frac{28}{-4}`
`VT=-7=VP`
b) `A=\frac{(1-\sqrt{a})^2-(\sqrt{a}+4)^2}{3+2\sqrt{a}}`
`A=\frac{1-2\sqrt{a}+a-a-8\sqrt{a}-16}{3+2\sqrt{a}}`
`A=\frac{-10\sqrt{a}-15}{3+2\sqrt{a}}`
`A=\frac{-5(2\sqrt{a}+3)}{3+2\sqrt{a}}`
`A=\frac{-5}{3+2\sqrt{a}}`
