Question

(y+7)^3+y(13-y^2)=21y^2+23

Answer 1

(y + 7)³ + y(13 - y²) = 21y² + 23
y³ + 21y² + 98y + 343 + 13y - y³ = 21y² + 23
-23 + 98y + 343 + 13y  = 21y² - 21y²
320 + 111y = 0
111y = -320
y = -320 / 111
y = -$frac{320}{111}$