🎓 MAH CET MCA📅 Year: 2025📚 Mathematics🏷 Differential Equation
4
A company models the rate of change of concentration by
$(y^2+3xy),dx+(x^2+xy),dy=0$, with $y=1$ when $x=1$. Find $y$ as a function of $x$ (choose the correct option).
$\text{Coeff}{x^n},(1+x)^{2n}=\binom{2n}{n}$ and $\text{Coeff}{x^n},(1+x)^{2n-1}=\binom{2n-1}{n}$.
$\displaystyle \binom{2n}{n}=\frac{(2n)}{n,n}=\frac{2n}{n}\cdot\frac{(2n-1)}{n,(n-1)}=2\binom{2n-1}{n}$.
So ratio $=2:1$.
🎓 MAH CET MCA📅 Year: 2025📚 Mathematics🏷 Parabola
1
The equation of a parabola is $y^2=4x$. Which of the following points lies on the parabola?
For $y^2=4x$, we need $x=\dfrac{y^2}{4}$.
For $y=\pm4$, $x=\dfrac{16}{4}=4$ $\Rightarrow$ $(4,4)$ and $(4,-4)$ satisfy.
Others give $x\neq\dfrac{y^2}{4}$.
🎓 MAH CET MCA📅 Year: 2025📚 Mathematics🏷 Properties Of Triangle
4
In $\triangle ABC$, sides are $a=9$, $b=7$, $c=12$. Find angle $C$ (opposite side $c$) using the Law of Cosines.
$\sqrt{1+\cos 2x}=\sqrt{2},|\cos x|$. On $\left[\frac{\pi}{2},\pi\right]$, $\cos x\le 0$ so $|\cos x|=-\cos x$.
LHS $=\sqrt{2},|\cos x|$, RHS $=\sqrt{2},|\cos x|$ only if $\cos^{-1}(\cos x)=|\cos x|$, which never holds for $x\in\left[\frac{\pi}{2},\pi\right]$.
Hence no real solution.
🎓 MAH CET MCA📅 Year: 2025📚 Mathematics🏷 Differential Equation
3
Given $,\dfrac{dy}{dx}+y=1,$ with $y(0)=2$, find $y(1)$.
Line passes through $A(6,7,7)$ with direction $\vec v=\langle3,2,-2\rangle$.
$\vec{AP}=\langle-5,-5,-4\rangle$. Distance $=\dfrac{\lVert \vec{AP}\times\vec v\rVert}{\lVert\vec v\rVert}=\dfrac{\sqrt{833}}{\sqrt{17}}=\sqrt{49}=7$.