# Elimination or Substitution and how do I do it?

^=exponent

Y^2=25
X^2-2x=4x+16

 jiten55 Posts: 106, Reputation: 59 Junior Member #2 Jan 22, 2008, 07:00 PM
Neither!

You have 2 unrelated equations.

From y^2 = 25 you get values of y

(Hint: if x^2 = 49, x = 7 or -7)

X^2-2x=4x+16

Becomes x^2 -6x -16 = 0

Which is a quadratic equations, which in this case can be solved by factorising, or
By the formula for quadratic equations.

Hint for factorising: Find 2 numbers (a and b) whose product is -16 and whose sum is -6.

Then factorising gives you (x -a) (x-b) = 0

From which you get 2 values of x: a and b.

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