Let a and b be the roots of the quadratic equation 2x2−10x+5=0.What is the value of (2a−3)(4b−6)?
Expanding the desired expression, we get (2a−3)(4b−6)=8ab−12a−12b+18=8ab−12(a+b)+18. This implies that we need the sum and product of the roots of the given equation, which are 10/2=5 and 5/2, respectively. Thus, the desired expression equals (8⋅52)−(12⋅5)+18=−22.