Answer:
To solve the inequality x^2-5x-36>0, we need to find the values of x for which the expression is greater than zero.
One way to do this is by factoring the quadratic expression:
x^2-5x-36 = (x-9)(x+4)
The expression is positive when either both factors are positive or both factors are negative.
When both factors are positive: x-9 > 0 and x+4 > 0
Solving for x, we get x > 9 and x > -4. Therefore, x > 9.
When both factors are negative: x-9 < 0 and x+4 < 0
Solving for x, we get x < 9 and x < -4. Therefore, x < -4.
Now, we have two intervals: x < -4 and x > 9. To check whether the expression is positive within these intervals, we can pick a value within each interval and plug it into the expression.
Let's choose x = -5 (within x < -4) and x = 10 (within x > 9).
For x = -5:
x^2-5x-36 = (-5)^2-5(-5)-36
= 25+25-36
= 14
Since 14 is greater than zero, the expression is positive when x = -5.
For x = 10:
x^2-5x-36 = 10^2-5(10)-36
= 100-50-36
= 14
Since 14 is greater than zero, the expression is also positive when x = 10.
Therefore, the solution to the inequality x^2-5x-36>0 is x < -4 or x > 9, which can be written in interval notation as (-∞,-4) ∪ (9,∞).