A student concluded that the solution to the equation √2x+1+3=0 is x=4.

Mathematics

2 answers:

Anna71 [15]3 years ago

5 0

Answer:

I do not agree, because x=4 is an extraneous

Step-by-step explanation:

First, to solve the equation, you subtract 3 from both sides, then square both sides, subtract one from both sides, and finally divide by 2 on both sides. This indeed gets us x=4, but we also need to check if it's an extraneous solution. To do that we simply plug in x=4 into the original equation. sqrt( 2(4) + 1 ) + 3 = 0. When we do this, we end up with ±3 + 3 = 0. I do not agree, because we don't know if the sqrt(9) is -3 or 3.

DerKrebs [107]3 years ago

5 0

Answer:

on Edge

Step-by-step explanation:

I do not agree with the student because there is no real solution.

Solving the equation only gives possible solutions, but you must check them in the original equation.

Checking the solution in the original equation shows that 4 is an extraneous solution.

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Let z = sin(x). This means z^2 = (sin(x))^2 = sin^2(x). This allows us to go from the equation you're given to this equation: 7z^2 - 14z + 2 = -5

That turns into 7z^2 - 14z + 7 = 0 after adding 5 to both sides. Use the quadratic formula to solve for z. The only solution is z = 1 (see attached image). Since we made z = sin(x), this means sin(x) = 1. All solutions to this equation will be in the form x = (pi/2) + 2pi*n, which is the radian form of the solution set. If you need the degree form, then it would be x = 90 + 360*n

The 2pi*n (or 360*n) part ensures we get every angle coterminal to pi/2 radians (90 degrees), which captures the entire solution set.

Note: The variable n can be any integer.