SOLUTION: Quadratic Equation 9. The area of a triangle is 20cm^2, and the altitude is 4cm greater than the base. Find the length of the base, to the nearest millimetre. Thanks!!!

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: Quadratic Equation 9. The area of a triangle is 20cm^2, and the altitude is 4cm greater than the base. Find the length of the base, to the nearest millimetre. Thanks!!!      Log On


   

Question 198389: Quadratic Equation
9. The area of a triangle is 20cm^2, and the altitude is 4cm greater than the base. Find the length of the base, to the nearest millimetre.
Thanks!!!
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
(1/2)ab=A
a=b+4
(1/2)b(b+4)=20
b^2+4b=40
b^2+4b-40=0
b^2+4b =40
b^2+4b+4=40+4 completing the square.
(b+2)^2=44
b+2=+-sqrt(44)
b=-2+-sqrt(11*4)
b=-2+-2sqrt(11)
b=-2+2sqrt(11) cm, b=-2-2sqrt(11) cm
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Ed