Question

a. Cho M' =  \(\sqrt{x+5}-\sqrt{x}=1\), Tính M = \(\sqrt{x+5}+\sqrt{x}\)

b. Cho  N' = \(\sqrt{25-x^2}-\sqrt{15-x^2}=2.\) Tính N = \(\sqrt{25-x^2}+\sqrt{15-x^2}\)

Answer 1

\(\left(\sqrt{x+5}-\sqrt{x}\right)\left(\sqrt{x+5}+\sqrt{x}\right)=\sqrt{x+5}+\sqrt{x}\)

=> \(x+5-x=M\Rightarrow M=5\)

b ) tương tự 

Answer 2

b) N.N' = \(\left(\sqrt{25-x^2}-\sqrt{15-x^2}\right).\left(\sqrt{25-x^2}+\sqrt{15-x^2}\right)=\left(25-x^2\right)-\left(15-x^2\right)=10\)

=> 2.N = 10 => N = 10:2 =5