The sum of two numbers is 15 and the sum of their squares is 113 Find the numbers.
Solution
Correct Answer: Option B
The sum of the numbers is 15 x + y = 15 or y = (15 - x); we can use this for substitution: "The sum of the squares is 113" x2 + y2 = 113 Substitute (15-x) for y in the above equation x2 + (15-x)2 = 113 x2 + 225 - 30x + x2 = 113 Arrange as a quadratic equation: x2+ x2 - 30x + 225 - 113 = 0 2x2 - 30x + 112 = 0 Simplify, divide by 2 x2 - 15x+56=0 => x2 -8x - 7x + 56 =0 => x(x-8)-7(x-8)=0 => (x-8)(x-7)=0 so, x= 8 or 7 when x = 8, then y=15-8=7 or, when x = 7, then y=15-7=8
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