SOLUTION: two squares have sides x cm and(x+4)cm .the sum of their areas is 656 sq.cm. express this as an algebraic equation in x and solve the equation to find the sides of the squares

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Question 761792: two squares have sides x cm and(x+4)cm .the sum of their areas is 656 sq.cm. express this as an algebraic equation in x and solve the equation to find the sides of the squares
Found 2 solutions by ramkikk66, josmiceli:
Answer by ramkikk66(644) About Me  (Show Source):
You can put this solution on YOUR website!
Area of 1st square = x%5E2
Area of 2nd square = %28x%2B4%29%5E2+=+x%5E2+%2B+8%2Ax+%2B+16
Sum of areas = x%5E2+%2B+x%5E2+%2B+8%2Ax+%2B+16+=+656
Simplifying and subtracting 656 from both sides
2%2Ax%5E2+%2B+8%2Ax+-+640+=+0
Dividing by 2
x%5E2+%2B+4%2Ax+-+320+=+0
This is a standard quadratic equation of the form ax^2 + bx + c = 0 with a = 1, b = 4 and c = -320.
Solving it using the quadratic solver (see below), we get the values of x as
x+=+16 or x+=+-20
Since x cannot be negative, x = 16
So, side of 1st square = highlight%2816%29 and side of second square = highlight%2820%29
Sum of areas = 256+%2B+400+=+656. Check!
:)
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation ax%5E2%2Bbx%2Bc=0 (in our case 1x%5E2%2B4x%2B-320+=+0) has the following solutons:

x%5B12%5D+=+%28b%2B-sqrt%28+b%5E2-4ac+%29%29%2F2%5Ca

For these solutions to exist, the discriminant b%5E2-4ac should not be a negative number.

First, we need to compute the discriminant b%5E2-4ac: b%5E2-4ac=%284%29%5E2-4%2A1%2A-320=1296.

Discriminant d=1296 is greater than zero. That means that there are two solutions: +x%5B12%5D+=+%28-4%2B-sqrt%28+1296+%29%29%2F2%5Ca.

x%5B1%5D+=+%28-%284%29%2Bsqrt%28+1296+%29%29%2F2%5C1+=+16
x%5B2%5D+=+%28-%284%29-sqrt%28+1296+%29%29%2F2%5C1+=+-20

Quadratic expression 1x%5E2%2B4x%2B-320 can be factored:
1x%5E2%2B4x%2B-320+=+1%28x-16%29%2A%28x--20%29
Again, the answer is: 16, -20. Here's your graph:
graph%28+500%2C+500%2C+-10%2C+10%2C+-20%2C+20%2C+1%2Ax%5E2%2B4%2Ax%2B-320+%29

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
The square with side = +x+ cm
has area +A%5B1%5D+=+x%5E2+ cm2
------------------------
The square with side = +x+%2B+4+ cm
has area +A%5B2%5D+=+%28+x%2B4+%29%5E2+ cm2
-------------------------------
given:
+A%5B1%5D+%2B+A%5B2%5D+=+x%5E2+%2B+%28+x+%2B+4+%29%5E2+
Let +A+=+A%5B1%5D+%2B+A%5B2%5D+
+A+=+x%5E2+%2B+%28+x+%2B+4+%29%5E2+
+A+=+x%5E2+%2B+x%5E2+%2B+8x+%2B+16+
+A+=+2x%5E2+%2B+8x+%2B+16+
+A+=+656+ cm2
+2x%5E2+%2B+8x+%2B+16+=+656+
+2x%5E2+%2B+8x+=+640+
+x%5E2+%2B+4x+=+320+ ( This is the equation )
I can complete the square
+x%5E2+%2B+4x+%2B+%28+4%2F2+%29%5E2+=+320+%2B+%28+4%2F2+%29%5E2+
+x%5E2+%2B+4x+%2B+4+=+324+
+%28+x+%2B+2+%29%5E2+=+18%5E2+
+x+%2B+2+=+18+
+x+=+16+
( There is also a solution +x%2B2+=+-18+, but ignore it )
+x+%2B+4+=+20+
The sides are 16 cm and 20 cm
check:
+A%5B1%5D+%2B+A%5B2%5D+=+x%5E2+%2B+%28+x+%2B+4+%29%5E2+
+A%5B1%5D+%2B+A%5B2%5D+=+16%5E2+%2B+20%5E2+
+A%5B1%5D+%2B+A%5B2%5D+=+256+%2B+400+
+A%5B1%5D+%2B+A%5B2%5D+=+656+
OK