Question
A Quadratic Word Problem.
The difference between two positive numbers is 3. The sum of the squares of the numbers is 89. Find the numbers.
The difference between two positive numbers is 3. The sum of the squares of the numbers is 89. Find the numbers.
Answers
a = first number
b = second number
a - b = 3 Add b to both sides
a - b + b = 3 + b
a = b + 3
a ^ 2 + b ^ 2 = 89
( b + 3 ) ^ 2 + b ^ 2 = 89
b ^ 2 + 2 * b * 3 + 3 ^ 2 + b ^ 2 = 89
b ^ 2 + 6 b + 9 + b ^ 2 = 89
2 b ^ 2 + 6 b + 9 = 89 Divide both sides by 2
b ^ 2 + 3 b + 9 / 2 = 89 / 2 Subtract 9 / 2 to both sides
b ^ 2 + 3 b + 9 / 2 - 9 / 2 = 89 / 2 - 9 / 2
b ^ 2 + 3 b = 80 / 2
b ^ 2 + 3 b = 40 Add 9 / 4 to both sides
b ^ 2 + 3 b + 9 / 4 = 40 + 9 / 4
b ^ 2 + 3 b + 9 / 4 = 160 / 4 + 9 / 4
b ^ 2 + 3 b + 9 / 4 = 169 / 4
________________________________________
Remark :
b ^ 2 + 3 b + 9 / 4 = ( b + 3 / 2 ) ^ 2
________________________________________
( b + 3 / 2 ) ^ 2 = 169 / 4 take sqrt to both sides
b + 3 / 2 = 13 / 2 Subtract 3 / 2 to both sides
b + 3 / 2 - 3 / 2 = 13 / 2 - 3 / 2
b = 10 / 2 = 5
a = b + 3 = 5 + 3 = 8
Nuumbers are :
5 and 8
Proof :
8 - 5 = 3
8 ^ 2 + 5 ^ 2 = 64 + 25 = 89
b = second number
a - b = 3 Add b to both sides
a - b + b = 3 + b
a = b + 3
a ^ 2 + b ^ 2 = 89
( b + 3 ) ^ 2 + b ^ 2 = 89
b ^ 2 + 2 * b * 3 + 3 ^ 2 + b ^ 2 = 89
b ^ 2 + 6 b + 9 + b ^ 2 = 89
2 b ^ 2 + 6 b + 9 = 89 Divide both sides by 2
b ^ 2 + 3 b + 9 / 2 = 89 / 2 Subtract 9 / 2 to both sides
b ^ 2 + 3 b + 9 / 2 - 9 / 2 = 89 / 2 - 9 / 2
b ^ 2 + 3 b = 80 / 2
b ^ 2 + 3 b = 40 Add 9 / 4 to both sides
b ^ 2 + 3 b + 9 / 4 = 40 + 9 / 4
b ^ 2 + 3 b + 9 / 4 = 160 / 4 + 9 / 4
b ^ 2 + 3 b + 9 / 4 = 169 / 4
________________________________________
Remark :
b ^ 2 + 3 b + 9 / 4 = ( b + 3 / 2 ) ^ 2
________________________________________
( b + 3 / 2 ) ^ 2 = 169 / 4 take sqrt to both sides
b + 3 / 2 = 13 / 2 Subtract 3 / 2 to both sides
b + 3 / 2 - 3 / 2 = 13 / 2 - 3 / 2
b = 10 / 2 = 5
a = b + 3 = 5 + 3 = 8
Nuumbers are :
5 and 8
Proof :
8 - 5 = 3
8 ^ 2 + 5 ^ 2 = 64 + 25 = 89
The product of two number is between 40 and 50. One number is 4 time less than the other
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