Problema Solution
find the quadratic equation whose roots are -3 and 1/5 and whose value at x =0 is -3.
Answer provided by our tutors
let the quadratic equation be
ax^2 + bx + c = 0, where a,b,c are constants
we know that for x=0 the value is -3 that is
a*0^2 + b*0 + c = -3
c = -3
Now we need to find a and b.
Since -3 and 1/5 are the roots if we replace for x = -3 or x = 1/5 the value must be 0 that is
for x = -3
a(-3)^2 - 3b - 3 = 0
9a - 3b - 3 = 0
for x = 1/5
a(1/5)^2 + b(1/5) - 3 = 0
a/25 + b/5 - 3 = 0
by solving the system of equations
9a - 3b - 3 = 0
a/25 + b/5 - 3 = 0
we find
a = 5
b = 14
therefore the quadratic equation is
5x^2 + 14x - 3 = 0