48=7x(x+3)

Solution for 48=7x(x+3) equation:

48=7x(x+3)

We move all terms to the left:

48-(7x(x+3))=0


We calculate terms in parentheses: -(7x(x+3)), so:

7x(x+3)

We multiply parentheses

7x^2+21x

Back to the equation:

-(7x^2+21x)


We get rid of parentheses

-7x^2-21x+48=0

a = -7; b = -21; c = +48;
Δ = b2-4ac
Δ = -212-4·(-7)·48
Δ = 1785
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{-(-21)-\sqrt{1785}}{2*-7}=\frac{21-\sqrt{1785}}{-14}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-21)+\sqrt{1785}}{2*-7}=\frac{21+\sqrt{1785}}{-14}
$