Problems on Numbers
1. Three times a positive number is less than its square by 54. Find the number.
Solution:
Let the number be x.
x2-3x=54
x2-9x+6x-54=0
(x-9)(x+6)=0
x=9, -6.
The number is 9.
2. Twice the square of a natural number is equal to the 30 more than the four times of that number. Find the number.
Solution:
Let the number be x.
2x2 =
4x+30
2x2-4x-30=0
x2-2x-15=0
x2-5x+3x-15=0
(x-5)(x-5)=0
x=5.
The number is 5.
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