SOLUTION: HELP PLEASE I DONT UNDERSTAND Solve: 3x^2-21x+30=0 20y^2+33y+10=0

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Question 849226: HELP PLEASE I DONT UNDERSTAND
Solve:
3x^2-21x+30=0
20y^2+33y+10=0

Answer by KMST(5328) About Me  (Show Source):
You can put this solution on YOUR website!
3x%5E2-21x%2B30=0 and 20y%5E2%2B33y%2B10=0 are quadratic equations.

Some quadratic equations can be simplified.
Dividing both sides of the equal sign by 3 we can transform
3x%5E2-21x%2B30=0 into the simpler equivalent equation
x%5E2-7x%2B10=0 .
That equation can be easily solved by factoring,
because x%5E2-7x%2B10=%28x-7%29%28x-3%29 ,
so we can rewrite x%5E2-7x%2B10=0 as the equivalent equation
%28x-7%29%28x-3%29=0 .
Then, if the product of %28x-7%29 and %28x-7%29 is zero,
either x-7=0 --> highlight%28x=7%29
or x-3=0 --> highlight%28x=3%29 .

20y%5E2%2B33y%2B10=0 cannot be simplified.
Maybe we could solve it by factoring, but it seems difficult.
For such a quadratic equation, I would use the quadratic formula.
The quadratic formula says that the solution to
ax%5E2%2Bbx%2Bc=0 , if it exists, is given by
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
20y%5E2%2B33y%2B10=0 is ax%5E2%2Bbx%2Bc=0 with y instead of x ,
a=20 , b=33 and c=10 so we try to calculate
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+ as

The solutions are:
y=%28-33%2B17%29%2F40=-16%2F40=highlight%28-2%2F5%29 or y=highlight%28-0.4%29
and
y=%28-33-17%29%2F40=-50%2F40=highlight%28-5%2F4%29 or y=highlight%28-1.25%29