SOLUTION: What are the solutions to the equation? x^2=-4x+21 Use the quadratic formula to solve: x^2+5x+1=0

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: What are the solutions to the equation? x^2=-4x+21 Use the quadratic formula to solve: x^2+5x+1=0      Log On


   

Question 955338: What are the solutions to the equation?
x^2=-4x+21
Use the quadratic formula to solve:
x^2+5x+1=0
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

1.
x%5E2=-4x%2B21
x%5E2%2B4x-21=0
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+ ...since a=1,b=4, and c=-21, we have
x+=+%28-4+%2B-+sqrt%28+4%5E2-4%2A1%2A%28-21%29+%29%29%2F%282%2A1%29+
x+=+%28-4+%2B-+sqrt%28+16%2B84+%29%29%2F2+
x+=+%28-4+%2B-+sqrt%28+100+%29%29%2F2+
x+=+%28-4+%2B-+10%29%2F2+
solutions:
x+=+%28-4+%2B+10%29%2F2+
x+=6%2F2+
x+=+3
and
x+=+%28-4+-+10%29%2F2+
x+=+-14%2F2+
x+=+-7+


2.
x%5E2%2B5x%2B1=0
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+ ...since a=1,b=5, and c=1, we have
x+=+%28-5+%2B-+sqrt%28+5%5E2-4%2A1%2A1+%29%29%2F%282%2A1%29+
x+=+%28-5+%2B-+sqrt%28+25-4+%29%29%2F2+
x+=+%28-5+%2B-+sqrt%28+21+%29%29%2F2+
exact solutions:
x+=+%28-5+%2B+sqrt%28+21+%29%29%2F2+
or
x+=+%28-5+-+sqrt%28+21+%29%29%2F2+
approximate solutions:
x+=+-0.2+
or
x+=+-4.8+