You add 7 to 19, so 26 and then divide it by 4.
X= 6.5
C=<span>1 is the answer my good man have a good day :)</span>
16x^4-81y^4 difference of perfect squares...
(4x^2-9y^2)(4x^2+9y^2) that's one of the equivalents...
(2x+3y)(2x-3y)(4x^2+9y^2) that's another one of them...
