Solve 7a^2-28=7(a^2-4)=

$$7 a ^ { 2 } - 28 = 7 ( a ^ { 2 } - 4 ) =$$

Solve for a (complex solution)

$$a\in \mathrm{C}$$

Solution Steps

Use the distributive property to multiply 7 by a^{2}-4.

$$7a^{2}-28=7a^{2}-28$$

Subtract 7a^{2} from both sides.

$$7a^{2}-28-7a^{2}=-28$$

Combine 7a^{2} and -7a^{2} to get 0.

$$-28=-28$$

Compare -28 and -28.

$$\text{true}$$

This is true for any a.

$$a\in \mathrm{C}$$

Solve for a

$$a\in \mathrm{R}$$

Solution Steps

Use the distributive property to multiply 7 by a^{2}-4.

$$7a^{2}-28=7a^{2}-28$$

Subtract 7a^{2} from both sides.

$$7a^{2}-28-7a^{2}=-28$$

Combine 7a^{2} and -7a^{2} to get 0.

$$-28=-28$$

Compare -28 and -28.

$$\text{true}$$

This is true for any a.

$$a\in \mathrm{R}$$