a. 3x- √ 4x²-12x+9 -7 =1
⇔ 3x - √ ( 2x-3)² -7 =1
⇔ 3x - | 2x-3 | -7 =1 ( với x≥0)
⇔ 3x - ( 2x -3) -7 =1
⇔ 3x -2x + 3-7=1
⇔ x-4=1
⇔x=5
b.√ 9x-27 -1/2 √4x-12 +2/5 √25x-75 + √x-3 =√50
⇔ √9( x-3) -1/2 √4(x-3) +2/5 √ 25( x-3) +√x-3 =√50
⇔ 3.√x-3 -1/2.2.√x-3 +2/5.5.√x-3 +√x-3 =√50
⇔ √x-3 ( 3-1+2+1) =√50
⇔ √x-3 .5 =√50
⇔√ x-3 .5 =√25.2
⇔ √ x-3 .5= 5.√2
⇔√x-3 =√2
⇔( √x-3)² =(√2)²
⇔ x-3=2
⇔x=5
