(d-5)(d+5)=39

Expand (d-5)(d+5) using the FOIL Method.

Apply the distributive property.

d(d+5)-5(d+5)=39

Apply the distributive property.

d⋅d+d⋅5-5(d+5)=39

Apply the distributive property.

d⋅d+d⋅5-5d-5⋅5=39

d⋅d+d⋅5-5d-5⋅5=39

Simplify terms.

Combine the opposite terms in d⋅d+d⋅5-5d-5⋅5.

Reorder the factors in the terms d⋅5 and -5d.

d⋅d+5d-5d-5⋅5=39

Subtract 5d from 5d.

d⋅d+0-5⋅5=39

Add d⋅d and 0.

d⋅d-5⋅5=39

d⋅d-5⋅5=39

Simplify each term.

Multiply d by d.

d2-5⋅5=39

Multiply -5 by 5.

d2-25=39

d2-25=39

d2-25=39

d2-25=39

Add 25 to both sides of the equation.

d2=39+25

Add 39 and 25.

d2=64

d2=64

Take the square root of both sides of the equation to eliminate the exponent on the left side.

d=±64

Simplify the right side of the equation.

Rewrite 64 as 82.

d=±82

Pull terms out from under the radical, assuming positive real numbers.

d=±8

d=±8

The complete solution is the result of both the positive and negative portions of the solution.

First, use the positive value of the ± to find the first solution.

d=8

Next, use the negative value of the ± to find the second solution.

d=-8

The complete solution is the result of both the positive and negative portions of the solution.

d=8,-8

d=8,-8

d=8,-8

Solve for d (d-5)(d+5)=39