how do you work out d2+3d-10=0?
there are several ways to solve this, but any quadratic equations, factorable or non-factorable, we use quadratic formula:
for a quadratic equation in the form ax^2 + bx + c = 0, we can solve the roots using the quadratic formula:
x = [-b +/- sqrt[b^2 - 4ac]] / (2a)
where the a, b are the numerical coefficients of x^2 and x respectively and c is the constant,,
*note: the +/- is plus or minus thus we can actually separate and solve it using + and -, so we have two roots
in the problem, we have
d^2+3d-10=0 , thus
a = 1
b = 3
c= -10
using quadratic formula,
d = [-b +/- sqrt[b^2 - 4ac]] / (2a)
d = [-3 +/- sqrt[3^2 - 4*1*(-10)]] / (2*1)
we separate this into plus and minus:
d = [-3 + sqrt[3^2 - 4*1*(-10)]] / (2*1)
which simplifies to d = 2
and the other,
d = [-3 - sqrt[3^2 - 4*1*(-10)]] / (2*1)
which simplifies to d = -5
hope this helps~ :)