Algerbra
posted by Margret on .
what is x if the problem is: (x+2)(x+4)=30+x

(x+2)(x+4) = 30 + x
first we expand the left side of the equation,, multiplying them,
x^2 + 2x + 4x + 8 = 30 + x
then we combine similar terms and make the right side of equation equal to zero (since it's quadratic equation) :
x^2 + 6x + 8  30  x = 0
x^2 + 5x  22 = 0
now, since it's not factorable, we use quadratic formula
x = [b + sqrt(b^2  4ac)]/(2a)
note: + is plus or minus
substituting,
x = [5 + sqrt(5^2  4(1)(22))]/(2*1)
x = [5 + sqrt(25 +88)]/2
x = [5 + sqrt(113)]/2
separating this into plus and minus:
x = [5 + sqrt(113)]/2 ; and
x = [5  sqrt(113)]/2
hope this helps~ :)