Question

1,thu gon bieu thuc

a A=\(\dfrac{a\sqrt{a}-8+2a-4\sqrt{a}}{a-4}\)

b,B=\(\dfrac{12\sqrt{6}}{\sqrt{7+2\sqrt{6}-\sqrt{7-2\sqrt{6}}}}\)

c, C=\(\dfrac{\sqrt{c^2+2c+1}}{\left|c\right|-1}\)

2,giai cac phuong trinh

a,\(x^2-9\sqrt{x}+14=0\)

b, \(\sqrt{3x^2-18x+28}+\sqrt{4x^2-24x+45}=-5-x^2+6\)

GIUP MINH VOI MINH CAN GAP

Answer 1

Cau 1: 

a: \(A=\dfrac{\left(\sqrt{a}-2\right)\left(a+2\sqrt{a}+4\right)+2\sqrt{a}\left(\sqrt{a}-2\right)}{a-4}\)

\(=\dfrac{\left(\sqrt{a}-2\right)\left(a+4\sqrt{a}+4\right)}{a-4}=\dfrac{\left(\sqrt{a}+2\right)^2}{\sqrt{a}+2}=\sqrt{a}+2\)

c: \(=\dfrac{\left|c+1\right|}{\left|c\right|-1}\)

TH1: c>0

\(C=\dfrac{c+1}{c-1}\)

TH2: c<0

\(C=\dfrac{\left|c+1\right|}{-\left(c+1\right)}=\pm1\)