x2 - 6x = 16 ∴ x2 - 6x + 9 = 25 ∴ (x - 3)2 = 25 ∴ x - 3 = 25 ∴ x = 28
If: x2+16 = 25 Then: x = 3
x2+4x+4 = 25 x2+4x+4-25 = 0 x2+4x-21 = 0 (x+7)(x-3) = 0 x = -7 or x = 3
5. A circle with centre (0,0) has equation: x2 + y2 = radius2 With: x2 + y2 = 25 = 52 The radius is 5.
We can't calculate what it equals until we know the value of ' x '.
x2 + 10x = 0 x2 + 10x + 25 = 25 (x + 5)2 = 25 x + 5 = +-5 x1 = 0 x2 =10
x2 - 6x = 16 ∴ x2 - 6x + 9 = 25 ∴ (x - 3)2 = 25 ∴ x - 3 = 25 ∴ x = 28
If: x2+16 = 25 Then: x = 3
25
x2+4x+4 = 25 x2+4x+4-25 = 0 x2+4x-21 = 0 (x+7)(x-3) = 0 x = -7 or x = 3
5. A circle with centre (0,0) has equation: x2 + y2 = radius2 With: x2 + y2 = 25 = 52 The radius is 5.
We can't calculate what it equals until we know the value of ' x '.
x2 - 10x + 25 = 0(x - 5)(x - 5) = 0x - 5 = 0x = 5
x2 + 2y = 52 + 2*2 = 25 + 4 = 29
9
Twenty-Five x2 + 10x = 8 x2 + 10x + 25 = 8 + 25 (x + 5)2 = 33
Rearrange: x2 - 10x + 25 = 0ie (x - 5)(x - 5) = 0x = 5Check: x2 = 25; 10x - 25 = 50 - 25 = 25. Job done