Q1Written answer
4(x–5) = 4x–5
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Worked solution
4(x- 5)= 4x – 20 ≠ 4x – 5 = RHS
The correct statement is 4(x-5) = 4x–20
NCERT · Class 8 · Maths
Chapter 14: Factorisation
Practice each question, then open the answer or worked solution.
Exercise 14.4
Textbook page 228 · 20 questionsQ2Written answer
x(3x+2) = 3x2+2
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Worked solution
LHS = x(3x+2) = 3x2+2x ≠ 3x2+2 = RHS
The correct solution is x(3x+2) = 3x2+2x
Q3Written answer
2x+3y = 5xy
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Worked solution
LHS= 2x+3y ≠ R. H. S
The correct statement is 2x+3y = 2x+3 y
Q4Written answer
x+2x+3x = 5x
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Worked solution
LHS = x+2x+3x = 6x ≠ RHS
The correct statement is x+2x+3x = 6x
Q5Written answer
5y+2y+y–7y = 0
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Worked solution
LHS = 5y+2y+y–7y = y ≠ RHS
The correct statement is 5y+2y+y–7y = y
Q6Written answer
3x+2x = 5x2
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Worked solution
LHS = 3x+2x = 5x ≠ RHS
The correct statement is 3x+2x = 5x
Q7Written answer
(2x) 2+4(2x)+7 = 2x2+8x+7
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Worked solution
LHS = (2x) 2+4(2x)+7 = 4x2+8x+7 ≠ RHS
The correct statement is (2x) 2+4(2x)+7 = 4x2+8x+7
Q8Written answer
(2x) 2+5x = 4x+5x = 9x
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Worked solution
LHS = (2x) 2+5x = 4x2+5x ≠ 9x = RHS
The correct statement is(2x) 2+5x = 4x2+5x
Q9Written answer
(3x + 2) 2 = 3x2+6x+4
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Worked solution
LHS = (3x+2) 2 = (3x)2+22+2x2x3x = 9x2+4+12x ≠ RHS
The correct statement is (3x + 2) 2 = 9x2+4+12x
Q10Written answer
Substituting x = – 3 in
(a) x2 + 5x + 4 gives (– 3) 2+5(– 3)+4 = 9+2+4 = 15
(b) x2 – 5x + 4 gives (– 3) 2– 5( – 3)+4 = 9–15+4 = – 2
(c) x2 + 5x gives (– 3) 2+5(–3) = – 9–15 = – 24
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Worked solution
(a) Substituting x = – 3 in x2+5x+4, we have
x2+5x+4 = (– 3) 2+5(– 3)+4 = 9–15+4 = – 2. This is the correct answer.
(b) Substituting x = – 3 in x2–5x+4
x2–5x+4 = (–3) 2–5(– 3)+4 = 9+15+4 = 28. This is the correct answer
(c) Substituting x = – 3 in x2+5x
x2+5x = (– 3) 2+5(–3) = 9–15 = -6. This is the correct answer