How do you solve 2y^2 + 10y = -11 2y2+10y=11?

1 Answer
Jul 7, 2016

y =-1.634 " or " y = -3.366y=1.634 or y=3.366

Explanation:

As it is a quadratic, first make it = 0.
2y^2 +10y +11 = 0 , " "ax^2 + bx + c =02y2+10y+11=0, ax2+bx+c=0

There are 3 options:
factorise - " " (this quadratic trinomial does not factorise)
completing the square (but a = 2, )
quadratic formula feels best for this one

y = (-b +-sqrt(b^2-4ac))/(2a) " with " a = 2, b= 10, c = 11y=b±b24ac2a with a=2,b=10,c=11

y = (-(10) +-sqrt(10^2-4(2)(11)))/(2(2))y=(10)±1024(2)(11)2(2)

y = (-10 +-sqrt(100-88))/4y=10±100884

y = (-10 +-sqrt12)/4y=10±124

We now solve it twice - once with + root and once with - root.
y = (-10 +sqrt12)/4 " or "y = (-10 -sqrt12)/4y=10+124 or y=10124

y =-1.634 " or " y = -3.366y=1.634 or y=3.366