We can write the quadratic expression 10x^2 + tx + 8 as:
10x^2 + tx + 8 = 10x^2 + (a+b)x + ab
where a and b are constants that we want to determine, and (a+b)x is the middle term in the quadratic expression.
We can factor 10 as 25 and 8 as 22*2, so we have:
10x^2 + tx + 8 = (2x + c)(5x + d)
where c and d are the constants that we need to determine.
Expanding the right-hand side of this equation, we get:
(2x + c)(5x + d) = 10x^2 + (2d+5c)x + cd
Comparing this to the original expression, we see that:
2d + 5c = t
cd = 8
We can use these equations to solve for c and d in terms of t:
c = (t - 2d)/5
d = 8/c
Substituting d in terms of c in the first equation, we get:
2(8/c) + 5c = t
Multiplying through by c, we get a quadratic equation in c:
16 + 5c^2 = tc
We want this equation to have real solutions for c, so the discriminant must be non-negative:
25t^2 - 80 >= 0
Solving this inequality for t, we get:
t <= -8/5 or t >= 8/5
Therefore, the quadratic expression 10x^2 + tx + 8 can be written as the product of two binomials for all values of t less than or equal to -8/5 or greater than or equal to 8/5.