90=49x(-1+7x)

Solution for 90=49x(-1+7x) equation:

90=49x(-1+7x)

We move all terms to the left:

90-(49x(-1+7x))=0

We add all the numbers together, and all the variables

-(49x(7x-1))+90=0


We calculate terms in parentheses: -(49x(7x-1)), so:

49x(7x-1)

We multiply parentheses

343x^2-49x

Back to the equation:

-(343x^2-49x)


We get rid of parentheses

-343x^2+49x+90=0

a = -343; b = 49; c = +90;
Δ = b2-4ac
Δ = 492-4·(-343)·90
Δ = 125881
The delta value is higher than zero, so the equation has two solutions
We use following formulas to calculate our solutions:
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}$

The end solution:

$\sqrt{\Delta}=\sqrt{125881}=\sqrt{49*2569}=\sqrt{49}*\sqrt{2569}=7\sqrt{2569}$
$x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(49)-7\sqrt{2569}}{2*-343}=\frac{-49-7\sqrt{2569}}{-686}
$
$x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(49)+7\sqrt{2569}}{2*-343}=\frac{-49+7\sqrt{2569}}{-686}
$