#mht-cet pcm
- The minimum value of \(z=2x+5y\) subject to \(x+y\ge4,\ x+3y\ge6,\ x,y\ge0\) is Answer: C. 11 Corner points of the (unbounded) region: (6,0)→12, (3,1)→11, (0,4)→20. Since both coefficients are positive, the minimum is 11... 1
- If \(y=x^x\), then \(\frac{dy}{dx}\) at \(x=e\) is Answer: B. 2e^e dy/dx=x^x(1+ln x) ; at x=e : e^e(1+1)=2e^e . 1
- Which alcohol gives turbidity immediately with Lucas reagent at room temperature? Answer: A. 2-methylpropan-2-ol Tertiary alcohols react immediately with conc. HCl/ZnCl₂ through a stable carbocation; 2-methylpropan-2-ol is... 1
- Which of the following is the strongest base in aqueous solution? Answer: C. (CH3)2NH In water, inductive effect, solvation and steric factors combine to give (CH₃)₂NH > CH₃NH₂ > (CH₃)₃N; aniline is much we... 1
- On prolonged heating with HI, glucose gives n-hexane. This shows that glucose Answer: B. has all six carbon atoms in a straight chain Complete reduction to n-hexane shows that the six carbons form an unbranched chain. 1
- Which of the following reactions has 100% atom economy? Answer: B. CH2=CH2 + H2 → C2H6 In an addition reaction all reactant atoms end up in the product, so the atom economy is 100%. 1
- Under identical conditions, the ratio of the rates of effusion of H2 and O2 is Answer: B. 4 : 1 Graham's law: fracr_(H_2)r_(O_2)=√(32/2)=4 . 1
- Ozonolysis of but-2-ene followed by treatment with Zn/H2O gives Answer: A. two molecules of ethanal CH₃CH=CHCH₃ is cleaved at the C=C bond to give 2 CH₃CHO. 1
- If \(x=a\cos^3t\) and \(y=a\sin^3t\), then \(\frac{dy}{dx}=\) Answer: A. -tan t dy/dx=3asin²tcos t/-3acos²tsin t=-tan t . 1
- If \(x^2+y^2=25\), then \(\frac{d^2y}{dx^2}\) at the point \((3,4)\) is Answer: D. -25/64 y'=-x/y=-3/4 ; y''=-y-xy'/y²=-4+9/4/16=-25/64 . 1
- The absolute minimum value of \(f(x)=x^3-3x\) on \([0,3]\) is Answer: C. −2 f'(x)=3x²-3=0⇒ x=1 . f(0)=0,\ f(1)=-2,\ f(3)=18 . Minimum =-2 . 1
- The equation of the tangent to \(y=x^2-2x+3\) at \(x=2\) is Answer: B. y=2x-1 Point (2,3); slope =2x-2=2 . Tangent: y-3=2(x-2)⇒ y=2x-1 . 1
- The numbers of σ and π bonds in acrylonitrile (CH2=CH–C≡N) are Answer: C. 6 σ and 3 π σ: 3 C–H + 1 (C=C) + 1 (C–C) + 1 (C≡N) = 6. π: 1 (C=C) + 2 (C≡N) = 3. 1
- The general solution of \(2\cos^2\theta+3\sin\theta=0\) is Answer: D. θ=nπ+(-1)ⁿ(-π/6),\ ninmathbb Z 2-2sin²θ+3sinθ=0⇒(2sinθ+1)(sinθ-2)=0⇒sinθ=-1/2 . 1
- The joint equation of the lines through the origin perpendicular to the lines \(x^2-5xy+4y^2=0\) is Answer: A. 4x²+5xy+y²=0 Given lines (x-y)(x-4y)=0 have slopes 1,1/4 . Perpendicular slopes -1,-4 : (x+y)(4x+y)=0 . 1
- The area of the parallelogram whose diagonals are \(3\hat i+\hat j-2\hat k\) and \(\hat i-3\hat j+4\hat k\) is Answer: B. 5sqrt3 vec d₁×vec d₂=-2hat i-14hat j-10hat k , magnitude √(300)=10sqrt3 . Area =1/2|vec d₁×vec d₂|=5sqrt3 . 1
- The vectors \(\hat i+2\hat j+3\hat k\), \(2\hat i+\hat j+\lambda\hat k\) and \(3\hat i+\hat j+2\hat k\) are coplanar if \(\lambda=\) Answer: C. 9/5 beginvmatrix1&2&3\\2&1&λ\\3&1&2endvmatrix=(2-λ)-2(4-3λ)+3(2-3)=5λ-9=0 . 1
- If \(|\vec a|=2\), \(|\vec b|=3\) and \(|\vec a+\vec b|=\sqrt{19}\), the angle between \(\vec a\) and \(\vec b\) is Answer: B. π/3 19=4+9+2vec a·vec b⇒vec a·vec b=3=6cosθ⇒cosθ=1/2 . 1
- The value of \(c\) in Lagrange's mean value theorem for \(f(x)=x^3\) on \([0,3]\) is Answer: D. sqrt3 3c²=27-0/3=9⇒ c=sqrt3in(0,3) . 1
- \(\int\frac{dx}{x^2+4x+13}=\) Answer: A. 1/3tan⁻¹(x+2/3)+C x²+4x+13=(x+2)²+3² ; use ∫dx/u²+a²=1/atan⁻¹u/a . 1
- \(\int e^x\left(\frac1x-\frac1{x^2}\right)dx=\) Answer: A. e^x/x+C Form ∫ e^x(f+f')dx=e^xf+C with f=1/x . 1
- The shortest distance between the lines \(\vec r=(\hat i+2\hat j+\hat k)+\lambda(\hat i-\hat j+\hat k)\) and \(\vec r=(2\hat i-\hat j-\hat k)+\mu(2\hat i+\hat j+2\hat k)\) is Answer: D. 3/sqrt2 vec b₁×vec b₂=-3hat i+3hat k (magnitude 3sqrt2 ); vec a₂-vec a₁=hat i-3hat j-2hat k ; d=|-3-6|/3sqrt2=3/sqrt2 . 1
- The angle between the line \(\frac{x-1}{2}=\frac{y+2}{1}=\frac{z}{2}\) and the plane \(2x-y+2z=5\) is Answer: C. sin⁻¹(7/9) sinθ=|vec b·vec n|/|vec b||vec n|=|4-1+4|/3·3=7/9 . 1
- The radius of a circle increases at 0.5 cm/s. The rate of increase of its area when the radius is 4 cm is Answer: A. 4π cm2/s dA/dt=2π rdr/dt=2π(4)(0.5)=4π . 1