TS Polycet (Polytechnic) 2021 Previous Question Paper with Answers And Model Papers With Complete Analysis

11)If α,β are the roots of a quadratic equation ax2+bx+c=0, a≠0 then \frac1\alpha+\frac1\beta = ……..

A) -\frac ba

B) \frac ca

C) -\frac bc

D) \frac bc

View Answer

C) -\frac bc
Explanation:We are given that α and β are roots of the quadratic equation: ax<sup>2</sup> + bx + c = 0, a ≠ 0 We need to find the value of:\frac{1}{α} + \frac{1}{β} Shortcut Trick:\frac{1}{α} + \frac{1}{β} = \frac{α + β}{α β} From the standard formulas for a quadratic:α + β = -\frac{b}{a}α β = \frac{c}{a} So,\frac{1}{α} + \frac{1}{β} = \frac{-\frac{b}{a}}{\frac{c}{a}} = -\frac{b}{c} Final Answer:-\frac{b}{c} Want a similar shortcut forα^2 + β^2? [/su_spoiler] </div>  <div class="mcq-question" data-answer="C"> <b>12)10th term of an arithmetic progression 2,-1,-4,...... is</b> <div class="mcq-options"> A) -21 B) -23 C) -25 D) -27 </div> [su_spoiler title="View Answer" style="fancy" icon="arrow"] C) -25 Explanation:We are given the arithmetic progression: 2,-1,-4,... Step 1: Identify first term and common difference First term a = 2 Common difference d = -1 - 2 = -3 Step 2: Use formula for nth term of AP: T<sub>n</sub> = a + (n-1)d For the 10th term: TT<sub>10</sub> = 2 + (10-1)(-3) = 2 + 9(-3) = 2 - 27 = -25 [/su_spoiler] </div>  <div class="mcq-question" data-answer="D"> <b>13)How many two digit numbers are divisible by 7?</b> <div class="mcq-options"> A) 10 B) 11 C) 12 D) 13 </div> [su_spoiler title="View Answer" style="fancy" icon="arrow"] D) 13 Explanation:To find how many two-digit numbers are divisible by 7, follow this shortcut method: Step 1: Two-digit numbers range from 10 to 99. Step 2: Find the first two-digit number divisible by 7:\lceil \frac{10}{7} \rceil = 2 ⇒ 2 × 7 = 14 Step 3: Find the last two-digit number divisible by 7:\lfloor \frac{99}{7} \rfloor = 14 ⇒ 14 × 7 = 98 Step 4: Use AP count formula:\text{Count} = \frac{(98 – 14)}{7} + 1 = \frac{84}{7} + 1 = 12 + 1 = 13[/su_spoiler] </div>  <div class="mcq-question" data-answer="B"> <b>14)The sum of 15 terms of A.P. 3, 6, 9......</b> <div class="mcq-options"> A) 315 B) 360 C) 415 D) 460 </div> [su_spoiler title="View Answer" style="fancy" icon="arrow"] B) 360 Explanation:We are given an A.P.:3, 6, 9, ... This is a common A.P. where: First terma = 3Common difference d = 6 - 3 = 3 Number of terms n = 15 Use shortcut formula for sum of n terms of A.P.:S_n = \frac{n}{2} [2a + (n – 1)d] Plug in values:S_{15} = \frac{15}{2} [2(3) + (15 – 1)(3)] = \frac{15}{2} [6 + 42] = \frac{15}{2} × 48 = 15 × 24 = 360[/su_spoiler] </div>  <div class="mcq-question" data-answer="C"> <b>15)The value of x which satisfies the equation 2x-(4-x)=5-x is</b> <div class="mcq-options"> A) 4.5 B) 3 C) 2.25 D) 0.5 </div> [su_spoiler title="View Answer" style="fancy" icon="arrow"] C) 2.25 Explanation:Solve: 2x - (4 - x) = 5 - x Simplify LHS: 2x - 4 + x = 5 - x ⇒ 3x - 4 = 5 - x Bring all terms to one side: 3x + x = 5 + 4 ⇒ 4x = 9 ⇒ x =\frac{9}{4} = 2.25 [/su_spoiler] </div>  <div class="mcq-question" data-answer="A"> <b>16)Solution of the equations 3x-4y=7 and 2x+3y=-1 is not equal to ......</b> <div class="mcq-options"> A)\frac{22}{22},\frac{33}{33} B)\frac{33}{33},-\frac{44}{44} C)\frac{44}{44},-\frac{77}{77} D)\frac{77}{77},-\frac{11}{11} </div> [su_spoiler title="View Answer" style="fancy" icon="arrow"] A)\frac{22}{22},\frac{33}{33}Explanation:Eliminate incorrect solution: You are given equations: ⇒1. 3x - 4y = 7 ⇒2. 2x + 3y = -1 Now test the options by substituting values. ⇒A.x = \frac{22}{22} = 1, y = \frac{33}{33} = 1 1st:3(1) – 4(1) = 3 – 4 = -1 ≠ 7 So, this is incorrect. Correct Answer:\frac{22}{22}, \frac{33}{33} (does notsatisfy the equations) [/su_spoiler] </div>  <div class="mcq-question" data-answer="A"> <b>17)If Σn = 45, then n= ......</b> <div class="mcq-options"> A) 9 B) 10 C) 11 D) 12 </div> [su_spoiler title="View Answer" style="fancy" icon="arrow"] A) 9 Explanation:If Σn = 45, then n = ? We assume this means the sum of first n natural numbers:\sum n = \frac{n(n+1)}{2} = 45
⇒ n(n+1) = 90 Try n = 9: 9 × 10 = 90 [/su_spoiler] </div>  <div class="mcq-question" data-answer="B"> <b>18)The centre of a circle with (1, 2) and (7,-4) as end points of the diameter is</b> <div class="mcq-options"> A) (-4,1) B) (4,-1) C) (-4,-1) D) (4,1) </div> [su_spoiler title="View Answer" style="fancy" icon="arrow"] B) (4,-1) Explanation:Midpoint of diameter endpoints (1, 2) and (7, -4) Use midpoint formula:\left( \frac{1 + 7}{2}, \frac{2 + (-4)}{2} \right) = \left( \frac{8}{2}, \frac{-2}{2} \right) = (4, -1) Correct Answer: (4, -1) [/su_spoiler] </div>  <div class="mcq-question" data-answer="A"> <b>19)Area of a triangle formed by the line xcosα+ysinα=p with the coordinate axes</b> <div class="mcq-options"> A)\frac{P^2}{2\sin\left(\alpha\right)\cos\left(\alpha\right)} B)\frac{P^2}{\sin\left(\alpha\right)\cos\left(\alpha\right)} C)\frac P{2\sin\left(\alpha\right)\cos\left(\alpha\right)} D)\frac P{\sin\left(\alpha\right)\cos\left(\alpha\right)} </div> [su_spoiler title="View Answer" style="fancy" icon="arrow"] A)\frac{P^2}{2\sin\left(\alpha\right)\cos\left(\alpha\right)}Explanation:Area of triangle formed by line with axes Equation: xcosα + ysinα = p Find x- and y-intercepts: Put y = 0:x = \frac{p}{\cosα} Put x = 0:y = \frac{p}{\sinα} Area of triangle =\frac{1}{2} \cdot \frac{p}{\cosα} \cdot \frac{p}{\sinα} = \frac{p^2}{2\sinα\cosα} Correct Answer:\frac{P^2}{2\sinα\cosα}$
20)If x+7y=7 and 7x-3y=-3, then y =

A) 1

B) 7

C) -3

D) 0

View Answer

A) 1
Explanation:Solve:
1) } x + 7y = 7
2) } 7x – 3y = -3
From (1):x = 7 – 7y
Substitute into (2):
7(7 – 7y) – 3y = -3
49 – 49y – 3y = -3 ⇒ -52y = -52 ⇒ y = 1
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