Solve for x and y: x ^2 +2y = 9,y = x + 3
- Replace y with x + 3. x^2 + 2(x+3) = 9
2) Expand the bracket, and subtract 9. x^2 + 2x - 3 = 0
3) Factorise the quadratic(x - 1)(x + 3) = 0
4) Therefore, x has 2 solutions. x = 1 and x = -3.
5) Find corresponding y solutions by substituting these values of x into the second equation. ==> x = 1, y = 4 and x = -3, y = 0
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There are 10 boys and 20 girls in a class. The mean mark for the class is 60, the mean mark for the girls is 54. Work out the mean mark for the boys.
