Find all numbers that must be excluded from the domain of the rational expression.?

The numbers that must be excluded from the domain are all the numbers that make the denominator = 0.

x^2+4x-45 = 0

(x+9)(x-5)= 0

so -9 and 5 must be excluded from the domain.

The denominator of this expression can never be equal to zero.

So we will factor the denominator in order to determine at what x values the denominator will be zero.

x^2 + 4x - 45 = 0

(x+9)(x-5)=0

x = -9, 5

Therefore x cannot equal -9 or 5.

so the domain is

D: {x | x ≠ -9, 5}

factor the denominator. The denominator can NOT be equal to zero.

(x^2+4x-45) = (x-9)(x+5)

neither of this may equal zero

x=9

or

x = -5

exclude ( 5, 9)

find all numbers that must be excluded from the domain of the rational expression- x+5/x^2+8x+7

Put x^2 +4x-45 =0

(x+9)(x-5) =0

or x =-9 and x=5

All real numbers except x =-9 and x=5 ..............Ans