Book Maths Puzzle

If 3x +7x=20 and xy=9,the value of 4x2+9y2 is?

Read Solution (Total 1)

3x +7x=20
10x=20
x=2
xy=9
y=9/x=9/2
4x^2+9y^2
=4*2^2+9*(9/2)^2=16+729/4=198.25
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The area of the bottom of a box is 192 cm2. If its height is 18.5 cm,its volume is ? The surface area of a cube is 24 cm2. Its volume is?