Question

Solve y2 = 15y − 56 using the quadratic formula.

Answer 1

`y^2 = 15y - 56\\\\y^2 - 15y + 56 = 0\\\\ (-b \pm √( b^2 -4( a)(c)) )/(2(a))\\\\ (15\pm √((-15)^2 -4(1)(56)) )/(2(1))\\\\ (15\pm √(1 ) )/(2)\\\\ (15\pm 1 )/(2)\\\\(16)/(2), (14)/(2)\\\\8, 7`

The solution is 7 and 8.

Answer 2

y^2= 15y -56
⇒ y^2 -15y+ 56= 0
⇒ y= \frac{-(-15)+ \sqrt{(-15)^2-4(1)(56)} }{2*1}
or y= \frac{-(-15)- \sqrt{(-15)^2-4(1)(56)} }{2*1}
⇒ y= 8 or y= 7

The final answer is y= 8 or y= 7~