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Differential Equations (Foundations)

Core skills for this exam family.

Phase 2 · AP Calculus

Differential Equations: core idea

dydx=ky⇒y=Cekx\frac{dy}{dx}=ky \Rightarrow y=Ce^{kx}.

Example problem: hint and answer

Solve y′=2xy'=2x, y(0)=0y(0)=0. Find y(3)y(3).

Hint: Integrate. Answer: 9.

Practice (9 problems — type your answers)

  • 1. Solve y′=3y'=3, y(0)=1y(0)=1. Find y(4)y(4).

  • 2. If y′=yy'=y and y(0)=2y(0)=2, find y′(0)y'(0).

  • 3. Slope field y′=x+yy'=x+y at (0,1)(0,1): slope?

  • 4. Equilibrium of y′=y(1−y)y'=y(1-y): larger one?

  • 5. Solve y′=cos⁡xy'=\cos x, y(0)=0y(0)=0. Find y(π/2)y(\pi/2).

  • 6. If y′=x2y'=x^2, find y′(2)y'(2).

  • 7. Solve y′=0y'=0, y(0)=5y(0)=5. Find y(10)y(10).

  • 8. Direction of y′=x−yy'=x-y at (1,0)(1,0): slope?

  • 9. If y′=1/xy'=1/x for x>0x>0, y(1)=0y(1)=0, find y(e)y(e).

Differential Equations Practice Problems — Foundations