Try the following GMAT Quantitative Reasoning question on how the coefficients of a quadratic equation impact the nature of the roots.
Question 71:

The values of $m$ for which the quadratic equation $4x^2 + x – mx + 1=0$ has real and equal roots are

1. $\quad -3 \; \textrm{and} \; -5$

2. $\quad -3 \; \textrm{and} \; 5$

3. $\quad 3 \; \textrm{and} \; -5$

4. $\quad 3 \; \textrm{and} \; 5$

5. $\quad -3 \; \textrm{only}$

 
Try the following GMAT Quantitative Reasoning question on manipulating linear equations to find value of an expression involving three variables.
Question 69:

Given $2x+y+z=3$ and $5x+3y+z=8$, what is the value of $x+y-z$ ?

1. $\quad -2$

2. $\quad -1$

3. $\quad 0$

4. $\quad 1$

5. $\quad 2$

 
Try the following GMAT Quantitative Reasoning question on manipulating and simplifying expressions with radical terms.
Question 67:

$\dfrac{(\sqrt{2})(\sqrt{5})}{(\sqrt{7}-\sqrt{2}-\sqrt{5})(\sqrt{7}+\sqrt{2}+\sqrt{5})}=$

1. $\quad -2$

2. $\quad -1$

3. $\quad -\dfrac{1}{2}$

4. $\quad \dfrac{1}{2}$

5. $\quad 1$

Try the following GMAT Quantitative Reasoning question on manipulating exponent expressions.

Question 65:

Suppose that $4^{x_1}=5$, $5^{x_2}=6$, $6^{x_3}=7$, $\ldots$ , $127^{x_{124}} = 128$. What is $x_1 x_2 \cdots x_{124}$ ?

1. $\quad 2$

2. $\quad \dfrac{5}{2}$

3. $\quad 3$

4. $\quad \dfrac{7}{2}$

5. $\quad 4$