The result of (x + a)(x + b) = x^2 + (a + b)*x + ab
The correct results for your problems are:
1. (x+5)(x+2) = x^2 + (5 + 2)x + (5*2) = x^2 + 7x + 10
2. (x-2)(x-2) = x^2 + (-2 - 2)x + (-2)*(-2) = x^2 - 4x + 4
3. (x-5)(x+12) = x^2 + (-5 + 12)x + (-5*12) = x^2 + 7x - 60
4. (3c-5d)(2c+4d) = 6c^2 + 12 cd - 10cd - 20d^2 = 6c^2 + 2cd - 20d^2
5. (5x-3)(3x-8) = 15x^2 - 40x - 9x + 24 = 15x^2 - 49x + 24
Use FOIL to complete these problems.
First (First item in each bracket multiplied together)
Outer (outside two items )
Inner (inside two items)
Last (last two items)
Your mistake on these was adding an x and the end of the last set on the first two problems. The Last two numbers to multiply for number 1 are
(x+5)(x+2) 5 and 2. 5x2 is 10, not 10x.