How do you solve sqrt(2x+1) - sqrt(x-5) = 3 2x+1x5=3?

1 Answer
Mar 27, 2016

x=21+-6sqrt(7)x=21±67

Explanation:

11. Start by moving -sqrt(x-5)x5 to the right side of the equation.

sqrt(2x+1)-sqrt(x-5)=32x+1x5=3

sqrt(2x+1)=3+sqrt(x-5)2x+1=3+x5

22. Since both sides contain radical signs, square both sides.

(sqrt(2x+1))^2=(3+sqrt(x-5))^2(2x+1)2=(3+x5)2

(sqrt(2x+1))(sqrt(2x+1))=(3+sqrt(x-5))(3+sqrt(x-5))(2x+1)(2x+1)=(3+x5)(3+x5)

33. Simplify.

2x+1=color(red)9+6sqrt(x-5)color(blue)+(color(blue)x2x+1=9+6x5+(x color(purple)(-5))5)

2x2x color(blue)(-x)+1x+1 color(red)(-9)9 color(purple)(+5)=6sqrt(x-5)+5=6x5

x-3=6sqrt(x-5)x3=6x5

44. Since the radical sign still exists on the right side of the equation, square both sides again.

(x-3)^2=(6sqrt(x-5))^2(x3)2=(6x5)2

(x-3)(x-3)=(6sqrt(x-5))^2(x3)(x3)=(6x5)2

55. Simplify.

x^2-6x+9=36(x-5)x26x+9=36(x5)

x^2-6x+9=36x-180x26x+9=36x180

66. Move all terms to the left side of the equation.

color(violet)1x^21x2 color(turquoise)(-42)x42x color(darkorange)(+189)=0+189=0

77. Use the quadratic formula to solve for xx.

color(violet)(a=1)color(white)(XXX)color(turquoise)(b=-42)color(white)(XXX)color(darkorange)(c=189)a=1XXXb=42XXXc=189

x=(-b+-sqrt(b^2-4ac))/(2a)x=b±b24ac2a

x=(-(color(turquoise)(-42))+-sqrt((color(turquoise)(-42))^2-4(color(violet)1)(color(darkorange)(189))))/(2(color(violet)1))x=(42)±(42)24(1)(189)2(1)

x=(42+-sqrt(1764-756))/2x=42±17647562

x=(42+-sqrt(1008))/2x=42±10082

x=(42+-12sqrt(7))/2x=42±1272

x=(2(21+-6sqrt(7)))/(2(2))x=2(21±67)2(2)

x=(color(red)cancelcolor(black)2(21+-6sqrt(7)))/(color(red)cancelcolor(black)2(1))

color(green)(|bar(ul(color(white)(a/a)x=21+-6sqrt(7)color(white)(a/a)|)))