# Are the following results correct:1. (x+5)(x+2) = x^2 + 7x + 10x. 2. (x-2)(x-2) = x^2 + 4x +4x 3. (x-5)(x+12) = x^2 + 7x - 60 4. (3c-5d)(2c+4d) = 6c^2 + 2cd^2 +20d^2 5. 5x-3)(3x-8) = 15x - 49x + 24

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### 2 Answers

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)

(**x**+5)(**x**+2)

Outer (outside two items )

(**x**+5)(x+**2**)

Inner (inside two items)

(x+**5**)(**x**+2)

Last (last two items)

(x+**5**)(x+**2**)

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.