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I need help solving this word problem relating to quadratic equations?
I don't understand what the words in the inverted comas mean, and please keep it as simple as possible i am pretty dumb
The perimeter of a square exceeds that of another by 100cm and "the area of the larger square exceeds three times the area of the smaller square by 325cm sq" .Find length of a side of each of the squares.
2 Answers
- ?Lv 77 years agoFavorite Answer
inverted com(m)as = quotation marks
let a = side of a square and b = side of another square, a and b both greater than 0
"The perimeter of a square exceeds that of another by 100cm"
The perimeter of a square is 4 times the length of a side
4a = 4b+100
"the area of the larger square exceeds three times the area of the smaller square by 325cm sq
The area of a square is the square of the length of a side
a² = 3b² + 325
You have two independent equations in two unknowns so you can solve them for the values of the unknowns.
4a = 4b+100 → a = b+25
a² = 3b² + 325 → (b+25)² = 3b² + 325
b² + 50b + 625 = 3b² + 325
2b² - 50b - 300 = 0
b² - 25b - 150 = 0
(b-30)(b+5) = 0
b = -5, 30 ← discard the negative value since b > 0
b = 30
Now that we know b, we can use the equation a = b+25 to find a
a = 30+25 = 55
We now know that the length of the side of the smaller square is 30cm and the length of the larger square is 55cm.
=====================================
Check:
Perimeter:
Pa = 4(55) = 220cm
Pb = 4(30) = 120cm
difference = 100cm ← Checks
Area:
Aa = 55² = 3025cm²
Ab = 30² = 900cm²
3025 - 3*900 = 325cm² ← Checks
- 7 years ago
Let, a and b be the sides of the two squares.
4b = 4a + 100
this implies that b = a + 25
b^2 = 3a^2 + 325
Substituting value of b in this 2nd equation, we get,
(a + 25)^2 = 3a^2 + 325
a^2 + 625 + 50a = 3a^2 + 325
2a^2 - 50a - 300 = 0
a^2 -25a - 150 = 0
a = {25 +- sqrt[25^2 - 4(1)(-150)]}/2
a = {25 +- 35}/2
a = 30, -5
but a can't be -ve, so a = 30
therefore, b = a + 25 = 30 + 25 = 55