Please guys please tell the answer if you know.. hurry up it's very important. Please tell the answer of questions no. 7and8
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manish421:
answer of question 7 is 16
ok
nope its322
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7) x-1/x = 4
=> squaring both sides
=> (x-1/x)² = 4²
=> x²+1/x²-2 = 16 (as , (a-b)² = a²+b²-2ab)
=> x²+1/x² = 16+2 = 18
now again squaring both sides
=> (x²+1/x²)² = (18)²
=> x⁴+1/x⁴+2 = 324 (as , (a+b)² = a²+b²+2ab)
=> x⁴+1/x⁴ = 324-2 = 322
8) i) (3x+4y)² = (3x)²+(4y)²+2(3x)(4y)
=> (3x+4y)² = 9x²+16y²+24xy
(as , (a+b)² = a²+b²+2ab)
ii) (7x-9z)² = (7x)²+(9z)²-2(7x)(9z)
=> (7x-9z)² = 49x²+81z²-126xz
as , (a-b)² = a²+b²-2ab
iii) (5x+4y)(5x-4y)
=> (a+b)(a-b) = a²-b²
=> (5x+4y)(5x-4y) = (5x)²-(4y)²
=> (5x+4y)(5x-4y) = 25x²-16y²
hope this helps
=> squaring both sides
=> (x-1/x)² = 4²
=> x²+1/x²-2 = 16 (as , (a-b)² = a²+b²-2ab)
=> x²+1/x² = 16+2 = 18
now again squaring both sides
=> (x²+1/x²)² = (18)²
=> x⁴+1/x⁴+2 = 324 (as , (a+b)² = a²+b²+2ab)
=> x⁴+1/x⁴ = 324-2 = 322
8) i) (3x+4y)² = (3x)²+(4y)²+2(3x)(4y)
=> (3x+4y)² = 9x²+16y²+24xy
(as , (a+b)² = a²+b²+2ab)
ii) (7x-9z)² = (7x)²+(9z)²-2(7x)(9z)
=> (7x-9z)² = 49x²+81z²-126xz
as , (a-b)² = a²+b²-2ab
iii) (5x+4y)(5x-4y)
=> (a+b)(a-b) = a²-b²
=> (5x+4y)(5x-4y) = (5x)²-(4y)²
=> (5x+4y)(5x-4y) = 25x²-16y²
hope this helps
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