Science (English Medium) Class 12 - CBSE Question Bank Solutions for Mathematics

\[\text { Find A and B so that y = A } \sin3x + B \cos3x \text { satisfies the equation }\]

\[\frac{d^2 y}{d x^2} + 4\frac{d y}{d x} + 3y = 10 \cos3x \] ?

\[\text { If }y = A e^{- kt} \cos\left( pt + c \right), \text { prove that } \frac{d^2 y}{d t^2} + 2k\frac{d y}{d t} + n^2 y = 0, \text { where } n^2 = p^2 + k^2 \] ?

\[\text { If y } = x^n \left\{ a \cos\left( \log x \right) + b \sin\left( \log x \right) \right\}, \text { prove that } x^2 \frac{d^2 y}{d x^2} + \left( 1 - 2n \right)x\frac{d y}{d x} + \left( 1 + n^2 \right)y = 0 \] Disclaimer: There is a misprint in the question. It must be 

\[x^2 \frac{d^2 y}{d x^2} + \left( 1 - 2n \right)x\frac{d y}{d x} + \left( 1 + n^2 \right)y = 0\] instead of 1

\[x^2 \frac{d^2 y}{d x^2} + \left( 1 - 2n \right)\frac{d y}{d x} + \left( 1 + n^2 \right)y = 0\] ?

\[\text { If y } = a \left\{ x + \sqrt{x^2 + 1} \right\}^n + b \left\{ x - \sqrt{x^2 + 1} \right\}^{- n} , \text { prove that }\left( x^2 + 1 \right)\frac{d^2 y}{d x^2} + x\frac{d y}{d x} - n^2 y = 0 \]

Disclaimer: There is a misprint in the question,

\[\left( x^2 + 1 \right)\frac{d^2 y}{d x^2} + x\frac{d y}{d x} - n^2 y = 0\] must be written instead of

\[\left( x^2 - 1 \right)\frac{d^2 y}{d x^2} + x\frac{d y}{d x} - n^2 y = 0 \] ?

If y = a x^{n + 1} + bx⁻ⁿ and \[x^2 \frac{d^2 y}{d x^2} = \lambda y\]  then write the value of λ ?

If x = a cos nt − b sin nt and \[\frac{d^2 x}{dt} = \lambda x\]  then find the value of λ ?

If x = t² and y = t³, find \[\frac{d^2 y}{d x^2}\] ?

If x = 2at, y = at², where a is a constant, then find \[\frac{d^2 y}{d x^2} \text { at }x = \frac{1}{2}\] ?

If \[y = 1 - x + \frac{x^2}{2!} - \frac{x^3}{3!} + \frac{x^4}{4!}\] .....to ∞, then write  \[\frac{d^2 y}{d x^2}\] in terms of y ?

If y = x + e^x, find \[\frac{d^2 x}{d y^2}\] ?

If y = |x − x²|, then find \[\frac{d^2 y}{d x^2}\] ?

If x = f(t) and y = g(t), then write the value of \[\frac{d^2 y}{d x^2}\] ?

If \[y = \left| \log_e x \right|\] find\[\frac{d^2 y}{d x^2}\] ?

If x = a cos nt − b sin nt, then \[\frac{d^2 x}{d t^2}\] is 

If x = at², y = 2 at, then \[\frac{d^2 y}{d x^2} =\] 

If y = axⁿ⁺¹ + bx⁻ⁿ, then \[x^2 \frac{d^2 y}{d x^2} =\] 

\[\frac{d^{20}}{d x^{20}} \left( 2 \cos x \cos 3 x \right) =\]

If x = t², y = t³, then \[\frac{d^2 y}{d x^2} =\] 

If y = a + bx², a, b arbitrary constants, then

If f(x) = (cos x + i sin x) (cos 2x + i sin 2x) (cos 3x + i sin 3x) ...... (cos nx + i sin nx) and f(1) = 1, then f'' (1) is equal to