SOLUTION: -x^2+7x=4 I changed it to -x^2+ 7x -4 = 0 and quadratic equation would be -b+/- the square root of b^2 -4ac all over 2a. a=-1 b= 7 c= -4 and I got 7.5 and 0.5 but when

Question 472171: -x^2+7x=4
I changed it to -x^2+ 7x -4 = 0
and quadratic equation would be -b+/- the square root of b^2 -4ac all over 2a.
a=-1
b= 7
c= -4
and I got 7.5 and 0.5 but when I plug it back in it does not work!
Help is MUCH appreciated!
Found 2 solutions by jim_thompson5910, mananth:
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!

Start with the given equation.

Notice that the quadratic is in the form of where , , and

Let's use the quadratic formula to solve for "x":

Start with the quadratic formula

Plug in , , and

Square to get .

Multiply to get

Subtract from to get

Multiply and to get .

or Break up the expression.

So the solutions are or

These solutions approximate to or

Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Find the roots of the equation by quadratic formula

a= -1 ,b= 7 ,c= -4

b^2-4ac= 49-(-16)
b^2-4ac= 33
= 5.74

x1=(-7+5.74)/-2
x1= 0.63
x2=(-7-5.74) / -2
x2= 6.37

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