x2 + 7x = 0 => x*(x + 7) = 0 => x = 0 or x + 7 = 0 so that x = 0 or x = -7
x=18
x2-4x-21 = 0 => x = -3 or x = 7 x2-3x-18 = 0 => x = -3 or x = 6
(2x)ysquared
3x2 = 21 describes two single values, and does not have an x intercept. 3x2 = 21 ∴ x2 = 7 ∴ x = ±√7
x2 = 6482 = 64x = 8
x2 + 3y = 7 3x + y2 = 3 3y = x2 + 7 y2 = -3x + 3 y = x2/3 + 7/3 y = ± √(-3x + 3) If you draw the graphs of y = x2/3 + 7/3 and y = ± √(-3x + 3) in a graphing calculator, you will see that they don't intersect, so that the system of the given equations has not a solution.
x: x2 - 81 = 0
A quadratic equation. If you wish to solve for x, you can do so as follows: -x2 + 6x + 7 = 0 x2 - 6x - 7 = 0 (x - 7)(x + 1) = 0 x ∈ {-1, 7}
x2 + 7x = 0 => x*(x + 7) = 0 => x = 0 or x + 7 = 0 so that x = 0 or x = -7
x=18
if x2 + 7 = 37, then x2 = 29 and x = ±√29
x2-4x-21 = 0 => x = -3 or x = 7 x2-3x-18 = 0 => x = -3 or x = 6
Factor the original equation to get (x-7)(x+2)=0, so x=7 or x=-2
x2-10 = 4x+11 x2-4x-10-11 = 0 x2-4x-21 = 0 (x+3)(x-7) = 0 x = -3 and x = 7
(2x)ysquared
3x2 = 21 describes two single values, and does not have an x intercept. 3x2 = 21 ∴ x2 = 7 ∴ x = ±√7