Question

hi please answer this



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Answer 1

Answer:

i think i no the answer

1. Given that xy=4

3x+7y=20

let us do squaring on both sides

(3x+7y)²=20²

(3x)²+(7y)²+ 2×3x×7y = 400 (since (a+b)²= a²+b²+2ab)

9x²+49y²+42xy=400

substitute xy=4

9x²+49y²+42×4=400

9x²+49y²+168=400

9x²+49y²=400-168

9x²+49y²=232

2. (0.1)²+(0.01)²/0.0001 -1

=0.01+0.0001/0.0001 -1

=0.0101/0.0001 -1

=101/10000 × 10000/1 -1

=101-1

=100

3. a+1/a=3

let us do squaring on both sides

(a+1/a)²=3²

a²+1/a²+2×a×1/a=9 ( since (a+b)²=a²+b²+2ab )

a²+1/a²+2=9

a²+1/a²=9-2

a²+1/a²=7

5. Given that ab=8

a+b=6

let us do squaring on both sides

(a+b)²=6²

a²+b²+2ab=36

substitute ab=8

a²+b²+2×8=36

a²+b²+16=36

a²+b²=36-16

a²+b²=20