Question 761135
The equation for the area of a rectangle is A = L x W
Equation 1: {{{45 = L*W}}}
Equation 2: {{{W = L - 4}}}
Plug (L-4) into equation 1 for W
{{{45 = L * (L - 4)}}}
Multiply the L through
{{{45 = L^2 - 4L}}}
Set the equation to zero by subtracting 45 from both sides
{{{0 = L^2 - 4L - 45}}}
You can now factor the equation by hand or use the quadratic equation.
*[invoke quadratic "L", 1,-4,-45]
The quadratic shows us that when L is equal to -5 and 9. Since we can not have a negative distance, 9 is th eonly answer that makes sense.
Now plug 9 into equation 2 for L
Equation 2: {{{W = L - 4}}}
{{{W = (9) - 4}}}
{{{highlight(W = 5)}}}
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L = 9m
W = 5m