Question

Which equations are correct? Select each correct answer. 5x4(4x2)=20x6 6a5(6a5)=36a25 3z7(4z2)=12z9 6b4(−3b4)=−18b8

Answer 1

Consider the given equations. We have to identify the correct equations.

1. $5x^4(4x^2) = 20x^6$

Using the laws of exponents, $a^m \times a^n = a^{m+n}$

Consider the LHS of the equation $5x^4(4x^2) = (5 \times 4) x^{4+2} = 20x^6$.

Therefore, this is the correct equation.

2. $6a^5(6a^5) = 36a^{25}$

Consider the LHS of the equation $6a^5(6a^5) = (6 \times 6) a^{5+5} = 36a^{10}$.

Therefore, this is not the correct equation.

3. $3z^7(4z^2) = 12z^{9}$

Consider the LHS of the equation $3z^7(4z^2) = (3 \times 4) z^{7+2} = 12z^{9}$.

Therefore, this is the correct equation.

4. $6b^4(-3b^4) = -18b^{8}$

Consider the LHS of the equation $6b^4(-3b^4) = (6 \times -3) b^{4+4} = -18b^{8}$.

Therefore, this is the correct equation.

Equations 1,3 and 4 are the correct equations.