Which of these is a solution of d^2y/dx^2 + 4y = 0?

Differential Equations · Question 22 of 67

Question 22

EasyOriginal question

Which of these is a solution of $\frac{d^2y}{dx^2} + 4y = 0$ ?

y = \sin 4x

Correct answerYour answer

y = e^{2 x}

Correct answerYour answer

y = \sin 2x

Correct answerYour answer

y = \cos x

Correct answerYour answer

Show the answer and explanation

CorrectNot quiteAnswer C

Correct answer: C

Try $y = \sin 2x$ : $y' = 2 \cos 2x$ and $y'' = - 4 \sin 2x$ .
Substituting makes both sides equal for every $x$ ; each of the others leaves something over.

Ten questions from Differential Equations, at your own pace.

Ten questions from Differential Equations, at your own pace.