Solve =0.8(x+3)(x-5)(x-7)

$$= 0.8 ( x + 3 ) ( x - 5 ) ( x - 7 )$$

Evaluate

$$\frac{4\left(x-7\right)\left(x-5\right)\left(x+3\right)}{5}$$

Solution Steps

Use the distributive property to multiply 0.8 by x+3.

$$\left(0.8x+2.4\right)\left(x-5\right)\left(x-7\right)$$

Apply the distributive property by multiplying each term of 0.8x+2.4 by each term of x-5.

$$\left(0.8x^{2}-4x+2.4x-12\right)\left(x-7\right)$$

Combine -4x and 2.4x to get -1.6x.

$$\left(0.8x^{2}-1.6x-12\right)\left(x-7\right)$$

Apply the distributive property by multiplying each term of 0.8x^{2}-1.6x-12 by each term of x-7.

$$0.8x^{3}-5.6x^{2}-1.6x^{2}+11.2x-12x+84$$

Combine -5.6x^{2} and -1.6x^{2} to get -7.2x^{2}.

$$0.8x^{3}-7.2x^{2}+11.2x-12x+84$$

Combine 11.2x and -12x to get -0.8x.

$$0.8x^{3}-7.2x^{2}-0.8x+84$$

Expand

$$\frac{4x^{3}}{5}-\frac{36x^{2}}{5}-\frac{4x}{5}+84$$

Solution Steps

Use the distributive property to multiply 0.8 by x+3.

$$\left(0.8x+2.4\right)\left(x-5\right)\left(x-7\right)$$

Apply the distributive property by multiplying each term of 0.8x+2.4 by each term of x-5.

$$\left(0.8x^{2}-4x+2.4x-12\right)\left(x-7\right)$$

Combine -4x and 2.4x to get -1.6x.

$$\left(0.8x^{2}-1.6x-12\right)\left(x-7\right)$$

Apply the distributive property by multiplying each term of 0.8x^{2}-1.6x-12 by each term of x-7.

$$0.8x^{3}-5.6x^{2}-1.6x^{2}+11.2x-12x+84$$

Combine -5.6x^{2} and -1.6x^{2} to get -7.2x^{2}.

$$0.8x^{3}-7.2x^{2}+11.2x-12x+84$$

Combine 11.2x and -12x to get -0.8x.

$$0.8x^{3}-7.2x^{2}-0.8x+84$$