Question: Solve 5x(3x+4)-5=0
Multiply out.
15x^2 + 20x - 5 = 0 --- divide everything by 5
3x^2 + 4x - 1 = 0 --- this doesn't factorise, so use the quadratic formula
x = (-4 +/- sqrt((4)^2 - 4*3*(-1)))/(2*3)
x = (-4 +/- sqrt(28))/6 = (1/3)(-2 +/- sqrt(7))
x = -2/3 + sqrt(7)/3. x = -2/3 - sqrt(7)/3