Question

Simplify these expressions and find their values if x = 3, a = – 1, b = – 2. (i) 3x – 5 – x + 9 (ii) 2 – 8x + 4x + 4 (iii) 3a + 5 – 8a + 1 (iv) 10 – 3b – 4 – 5b (v) 2a – 2b – 4 – 5 + a

Answer 1

(i) 3x–5–x+9 = 3x-x-5+9 = 2x+4 = 2×3+4 = 6+4 = 10 [putting a = 3]

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(ii) 2–8x+4x+4 = -8x+4x+2+4 = -4x+6 = -4×3+6 = -12+6 = -12 [putting a = 3]

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(iii) 3a+5–8a+1 = 3a-8a+5+1 = -5a+6 = -5(-1)+6 = 5+6 = 11 [putting a = -1]

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(iv) 10–3b–4–5b = -3b-5b+10-4 = -8b+6 = -8(-2)+6 = 16+6 = 22 [putting a = -2]

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(v) 2a–2b–4–5+a = 2a+a-2b-4-5 = 3a-2b-9 = 3(-1)-2(-2)-9 = -3+4-9 = -8 [putting a = -1, b = -2]