(x-1)(3x)=(8)(21)

Solution for (x-1)(3x)=(8)(21) equation:

(x-1)(3x)=(8)(21)

We move all terms to the left:

(x-1)(3x)-((8)(21))=0

determiningTheFunctionDomain
(x-1)3x-821=0

We multiply parentheses

3x^2-3x-821=0

a = 3; b = -3; c = -821;
Δ = b2-4ac
Δ = -32-4·3·(-821)
Δ = 9861
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-3)-\sqrt{9861}}{2*3}=\frac{3-\sqrt{9861}}{6}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-3)+\sqrt{9861}}{2*3}=\frac{3+\sqrt{9861}}{6}
$